STUDY PROTOCOL Open AccessThe Amsterdam Sexual Abuse Case .docx

STUDY PROTOCOL Open Access
The Amsterdam Sexual Abuse Case (ASAC)-study
in day care centers: longitudinal effects of sexual
abuse on infants and very young children and
their parents, and the consequences of the
persistence of abusive images on the internet
Ramón JL Lindauer1,2*, Sonja N Brilleslijper-Kater3, Julia
Diehle1, Eva Verlinden1,4, Arianne H Teeuw3,
Christel M Middeldorp5,6, Wilco Tuinebreijer4, Thekla F
Bosschaart3, Esther van Duin1,2 and Arnoud Verhoeff4,7
Abstract
Background: Little research has been done on the signs of child
sexual abuse (CSA) in infants and very young
children, or on the consequences that such abuse – including the
persistence of the abusive pornographic images
on the internet – might have for the children and their parents.
The effects of CSA can be severe, and a variety of
risk- and protective factors, may influence those effects. CSA
may affect the psychosocial-, emotional-, cognitive-,
and physical development of children, their relationships with
their parent(s), and the relations between parents. In
the so called ‘the Amsterdam sexual abuse case’ (ASAC),
infants and very young children were victimized by a
day-care employee and most of the victims were boys. Research
involving the children and their parents would
enable recognition of the signs of CSA in very young children
and understanding the consequences the abuse
might have on the long term.

Methods/design: The proposed research project consists of three
components:
(I) An initial assessment to identify physical- or psychological
signs of CSA in infants and very young children who
are thought to have been sexually abused (n = 130);
(II) A cross-sequential longitudinal study of children who have
experienced sexual abuse, or for whom there are
strong suspicions;
(III) A qualitative study in which interviews are conducted with
parents (n = 25) and with therapists treating children
from the ASAC. Parents will be interviewed on the perceived
condition of their child and family situation, their
experiences with the service responses to the abuse, the effects
of legal proceedings and media attention, and the
impact of knowing that pornographic material has been
disseminated on the internet. Therapists will be
interviewed on their clinical experiences in treating children
and parents.
The assessments will extend over a period of several years. The
outcome measures will be symptoms of
posttraumatic stress disorder (PTSD), dissociative symptoms,
age-inappropriate sexual behaviors and knowledge,
behavioral problems, attachment disturbances, the quality of
parent–child interaction, parental PTSD, parental
(Continued on next page)
* Correspondence: [email protected]
1Department of Child and Adolescent Psychiatry, Academic
Medical Centre,
Amsterdam, The Netherlands
2De Bascule, Academic Center for Child and Adolescent
Psychiatry,
Amsterdam, The Netherlands
Full list of author information is available at the end of the
article

© 2014 Lindauer et al.; licensee BioMed Central Ltd. This is an
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reproduction in any medium, provided the original work is
properly credited. The Creative Commons Public Domain
Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to
the data made available in this article,
unless otherwise stated.
Lindauer et al. BMC Psychiatry 2014, 14:295
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(Continued from previous page)
partner relation, and biological outcomes (BMI and DNA).
Discussion: The ASAC-project would facilitate early detection
of symptoms and prompt therapeutic intervention
when CSA is suspected in very young children.
Keywords: Sexual abuse, Infants, Very young children, Signs,
Effects, Internet
Background
Problem definition
In late 2010, the Dutch Public Prosecution Service dis-
closed that a suspected 130 infants and very young chil-
dren had been sexually abused by a male employee of an

Amsterdam day care center. The episode had an enor-
mous impact and drew considerable media attention at
home and abroad. This article describes the longitudinal
and qualitative study we have now started, which will
monitor the abused children over a longer period of time.
International prevalence statistics indicate that 4 to
127 of 1,000 children or adolescents may be involved in
child sexual abuse (CSA), depending on the type of in-
formant and the child’s gender [1-7]. Prevalence figures
are higher for girls than for boys, and 25% to 35% of the
sexual abuse affects children younger than seven years
of age [3].
CSA may produce short-, medium-, and long terms ef-
fects in children and parents [8-16]. In the short term,
children may develop posttraumatic stress disorder
(PTSD), problems with sexuality or sexual behavior, dis-
sociative symptoms, psychosomatic complaints, emotional
problems, anxieties, and sleep disturbances [17-31]. In the
middle term (two to four years after abuse has ceased),
parents report that one half of the children still have fears
relating to the threat from the perpetrator(s) [32] and that
one half still have serious PTSD symptoms [33]. In the
long term, sexually abused children have been found to
have a three times higher risk of developing mental
health- and physical problems than non-abused children
[34-39]. Research has shown that childhood traumatic and
stressful experiences can lead to chronic health problems
in later life, including cardiovascular disease, obesity, and
diabetes [40,41]. An Australian study (N = 2688) on the
long-term effects of CSA demonstrated that about one
quarter of the victims required mental health care over
the course of a 43-year period, as compared to 8% of the
control group [36].
If children who have experienced CSA develop serious

health consequences it is partly connected to a range of
risk- and protective factors. Risk factors involve the nature
of the abuse (penetration makes it worse), the duration
and frequency, the amount of violence used, and whether
the perpetrator was a family member or relative [42-44].
Protective factors include parental support (if the abuse
was outside the family).
A child’s temperament also influences whether or not
symptoms develop. Although PTSD is always preceded
by an environmental factor – the traumatic event – twin
studies indicate that genetic factors have a 30%-40% in-
fluence on individual differences in susceptibility [45,46].
This is comparable to the heritability of other disorders
such as depression, yet for PTSD far less research has
investigated the influence of genes on the onset of the
disorder [47].
Excessive, repeated, or chronic stress in the initial
years of life can deregulate the biological stress systems
and induce epigenetic modifications – structural changes
in DNA that make the DNA at that locus easier or more
difficult to read. This affects the degree of expression of
a gene, meaning that the risk of developing PTSD symp-
toms may be influenced not just by congenital genetic
variation, but also by epigenetic modifications induced
by the trauma [48].
Parents face the awesome task of dealing with their
own reactions and feelings without distressing their child
any further [49]. Common parental reactions are feelings
of guilt, rage against the perpetrator, and fear that the
abuse will be repeated in a different setting [50]. Parents
have reported that being informed about the sexual
abuse of their child, the police questioning, and the

media attention are all highly stressful [33]. Parents may
develop PTSD and depressive symptoms themselves
[50-56]. This can adversely affect their relationships with
their child, their partner, and the child’s siblings [57-59].
For young children, the quality of the attachment relation-
ship with parents is important for their further develop-
ment. Traumatic experiences, including sexual abuse, may
alter the quality of the attachment relationship to parents;
it may become insecure or even disorganized. Alterna-
tively, parental care may have protective effects, with pos-
sible positive influences on biological processes such as
epigenetic modifications or alterations in the functioning
of the HPA axis [45,46,60-66]. Reduced coping capacities
and parental concerns about issues such as sexual devel-
opment (including homosexuality in abused boys) have
been found to often raise new problems for families. In
about 20% of cases, a negative spiral emerges that leads to
prolonged psychopathology in the child and possibly in
the parents.
If child pornography has been made the children
are not only victims of the CSA they have suffered,
Lindauer et al. BMC Psychiatry 2014, 14:295 Page 2 of 12
but also of the fact that recorded images of the abuse
persist [67-69]. The existence of such material can
have traumatic effects on the child and the family as
well giving the gross violation of their privacy [69]. If
the abusive images have been placed on the internet,
the children and their parents must live with the
permanence of the images, since it is virtually impos-
sible to ever completely remove them. The realiza-

tion of that permanence, which often does not dawn
until later, may trigger feelings of loss of control, help-
lessness, shame, and fear [69]. At present, little is known
about what consequences the dissemination of por-
nographic material might have for the victimized chil-
dren, or their parents. Only a few treatment programs
exist that focus on these aspects of the victims’ ex-
perience [67].
In view of the probable serious consequences of CSA
in the short-, medium-, and long terms, it is important
to ensure early recognition of symptoms and prompt
provision of support. Research literature about physical
symptoms that might confirm suspicions of sexual abuse
in pre-school children is very limited [70-73]. No valid
diagnostic instruments are currently available. Barely
any research has been conducted on the impact of CSA
in the group of infants and very young children, usually
this group is subsumed under a broader category labeled
‘younger than 6’ or ‘younger than 12’. Many children
who are at risk of CSA are still in the preverbal phase
which means that their expressive capabilities are limited
[74-77]. Few specific details are known about the clinical
picture for very young traumatized children. The limited
research on physical injury in young children for whom
a strong suspicion of CSA exists has found that just 4%
to 14% of the children show signs of physical injury
[70,78-80].
Although CSA is common, it does rarely occur on the
scale that it did in the Amsterdam sexual abuse case,
committed by one chief perpetrator with one or two
possible accomplices, and the severity of CSA is well
documented by the police. CSA has grave consequences
for the children involved, their parents, and their fa-
milies. The quality of the parent–child relationship may

be a protective factor. Systematic research on the effects
that CSA has on very young children, and on boys in
particular, is urgently needed to better understand the
psychological and physical clinical presentations of such
abuse and to identify the risk- and protective factors
for psychopathology resulting from it. This know-
ledge will enable early recognition of problems and early
intervention.
Research questions and objectives
The purpose of the study is to systematically document
the signs and symptoms of sexual abuse in infants and
very young children and the short-, medium-, and long-
term effects of the abuse, including the effects of the
persistence of pornographic internet images, on the chil-
dren and their parents. The study will examine the psy-
chological, social, emotional, cognitive, and physical
development, and developmental problems, of children,
the psychological well-being of their parents, and the qual-
ity of interactions between parents and children, and be-
tween parents. The outcome measures will be symptoms
of PTSD, dissociative symptoms, age-inappropriate sexual
behavior and knowledge, behavioral problems, attachment
disturbances in children, PTSD in parents, the quality of
parent–child interaction, parental partner relation, and
biological outcomes.
We will investigate the following types of questions:
� Child-focused questions:
✓ What signs of sexual abuse of infants and very
young children are apparent in the short term?
■ What physical injuries do very young sexually
abused children have?
■ Does a relationship exist between the severity
of the abuse (judged from information in police

reports and criminal indictments) and the
development of trauma symptoms in children?
■ Does a relationship exist between parents’
own past experiences of abuse and the
development of trauma symptoms in their
children?
✓ How does sexuality and sexual knowledge
develop in children for whom early sexual abuse
has been confirmed or strongly suspected?
✓ What effects of early-age sexual abuse are
apparent in the medium- and long terms, and to
what extent are these influenced by biological
factors?
✓ What consequences does the persistence of
pornographic internet images have for a child in
medium and long terms?
� Parent-focused questions:
✓ What psychological consequences are
experienced by parents whose child has been
abused?
✓ What consequences does the persistence of
pornographic Internet images have for parents in
the medium and long terms?
✓ What influence does the sexual abuse have on
parental partner relationships?
� Influences of parent–child interaction and family
environment:
✓ What risk- and protective factors influence the
development of symptoms in children and their
parents for example social support, attachment
problems, parental trauma history?

✓ What influence does the quality of the parent–
child relationship have on the development of
symptoms in the children?
� Additional questions:
✓ What are the experiences of parents who have,
and who have not, informed their child about the
sexual abuse the child experienced as an infant? If
they have informed the child, how and at what age
did they do so? What underlying motives do
parents have for informing or not informing their
children?
✓ What clinical experiences are reported by
therapists that treat children and parents for the
effects of sexual abuse?
Methods/Design
Project organization
The following people and groups will be involved in the
study: the project leaders, the project group, and a re-
search advisory committee comprised of Dutch and inter-
national experts.
The project group will support the three project
leaders (RJLL, SNB and AV) in all facets of the study.
The project leaders will have charge of the day-to-day
practical conduct of the study. The project leaders and
the members of the project group will meet regularly.
The research advisory committee will be informed once
a year in writing and will make recommendations to the
project group. Should the subject matter of the study re-
quire more consultation, meetings will be scheduled

more frequently.
Study design
Signs of sexual abuse in very young children
The initial assessment (T0) took place shortly after dis-
closure of the abuse case in December, 2010. At the
Academic Medical Centre (AMC), five outpatient teams
were appointed, composed of three types of profes-
sionals (pediatrician, parent adviser, and child psycho-
logist or child development expert). Each team made
systematic diagnoses of the physical and psychological
effects of sexual abuse (confirmed or suspected) in chil-
dren and their parents. A total of 130 children and
their parents were examined; in 126 cases, parents
authorized the use of anonymized data for research
purposes. For 87 of the children, a criminal case file
now exists in which sexual abuse has been demon-
strated by investigators and/or acknowledged by the
chief perpetrator.
Longitudinal (cross-sequential) study
We will conduct a cross-sequential longitudinal study
[81,82] involving children who have experienced sexual
abuse or for whom there are strong suspicions of abuse.
A cross-sequential longitudinal design will enable us to
systematically determine the effects of sexual abuse by
combining three research techniques: (1) examining the
same children at different ages (longitudinal study); (2)
examining children of different ages at the same point in
time (cross-sectional study); and (3) examining children
of different ages at different points in time (cross-se-
quential study). The longitudinal study started in 2013
(T1). Some children who have experienced sexual abuse
or for whom there are strong suspicions of abuse were
not involved in the measurements of T0. However, their

parents had contact with the Public Health Service dur-
ing the second aftercare phase as part of the psycho-
social support program for accidents and disasters. The
Public Health Service provided this aftercare program
with the goal to detect psychosocial complaints in trau-
matized victims. The research project will monitor chil-
dren and their parents for several years (granted till
2017) to gather firm evidence on long-term effects.
Qualitative study
In the qualitative study, parents and therapists will be
interviewed by a psychologist/researcher. The focus of
the parental interviews will be on the perceived con-
dition of their child, their family situation, their expe-
riences with the health and social services, the impact
of legal procedures and media attention, the impact
of the Internet dissemination of the child pornogra-
phic material, and the extent to which they recognize
outcomes of the quantitative study. The focus of the
interviews of the therapists will be on their experi-
ences of treating children and parents involved in the
abuse case.
Study groups
This group involves the children who have experienced
sexual abuse or for whom there are strong suspicions of
abuse (n = 126).
Longitudinal study (cross-sectional)
The study group as known at the AMC (n = 126), com-
prised very young children from 4.5 months to 11.2 years
of age (median age 3.9 years; 77 boys and 48 girls) who
are confirmed or strongly suspected to have experienced
sexual abuse (oral, vaginal, and/or anal). Confirmed sex-
ual abuse is defined as abuse that has been demonstrated

by police and/or affirmed by the chief perpetrator. Some
children who are confirmed or strongly suspected to
have experienced sexual abuse were not involved in the
AMC study group (n = 126) but had contact with the
Public Health Service during the aftercare program.
Therefore we proceed on the assumption that parents of
150 children can be contacted for participation in this
research project.
Qualitative study
This group will involve a subgroup of participating par-
ents. Following the first quantitative assessment in the
longitudinal study (T1), parents will be recruited for
qualitative interviews (n = 25; this number will suffice
for the qualitative data, as we expect no new information
from a larger sample). To recruit the interviewees, we
will first compile a comprehensive list of parents who
have expressed willingness to take part. From this list,
we will select parents for the interviews. In this selec-
tion, it will be important to allow for gender, education,
SES, ethnicity, and the age at which their child was
abused. Therapists from various child and adolescent
mental health care agencies will also be selected for
interviews.
Informed consent
The Medical Ethical Committee of the Academic Medical
Centre, Amsterdam, the Netherlands approved on the
research protocol.
At T0, we requested parents’ permission to use the

collected data in anonymized form for publication in
scholarly journals. After consultation with the medical
director, we requested this consent orally and recorded
it in the medical file. At the start of the longitudinal
study (T1), parents will be requested to also provide
written consent for T0.
Parents who took part in the T0 measure will be con-
tacted by or in behalf of AMC-employees who were in-
volved in the T0 measure. Parents will be asked if the
Public Health Service may inform them about this longi-
tudinal research project. Parents who are known to the
Public Health Service from the second aftercare phase in
2011 will again be contacted by or in behalf of Public
Health Service employees who were involved in the after
care phase. Parents will be asked if they want to receive
information about the longitudinal research project. Par-
ents who want to receive information will be sent writ-
ten information about the research study. If necessary,
researchers will provide more detailed explanations in
response to any parental questions. After a couple of
days, written consent to participate will be requested.
Separate written consent will be obtained from parents
who are willing to take part in the study component in
which children are also actively involved. Children who
are older than 7 and who actively take part in the study
will also be provided with information about the re-
search. Children who are older than 11 will also be asked
to sign an informed consent form. Children who are not
informed about the sexual abuse will not be contacted for
this research project. A separate written consent form will
be requested from participants who also agree to bio-
logical testing.
The reason we have decided on the tiered informed

consent procedure is to enable parents to take part in
the project who do not wish to inform their child about
the abuse. In those cases, we will contact the parents
only, and will administer questionnaires and interviews
to them about their child.
For examination of police files separate informed con-
sent will be asked. Informed consent will also be asked
for information about the received treatment and the
effects.
Assessments
In the present project we describe how we will monitor
the children and their parents over a period of many years.
This will depend on the ongoing consent of parents (and
of children, if aged 12 or older). A number of assessments
will take place: T0 (late 2010), T1 (2013), T2 (2014), T3
(2015), T4 (2016), T5 (2017), and T6 (2018).
Assessment instruments
Background variables: demographic information, sever-
ity and type of sexual abuse, other stressors, family prob-
lems, legal procedures, and psychological treatment and
its effects.
The following assessment instruments were
administered at T0 (late 2010):
� Adams classification for genital abnormalities after
sexual abuse [83-86]. Photographs of the external
genitals were made in the “frog-leg” position
(supine with knees bent and foot soles together)
and the “polar bear” position (on knees and
elbows). The pictures were taken in conformity

with the guidelines for identifying physical signs
of suspected sexual abuse and were assessed by a
team of experts using the Adams classification.
The interrater reliability of these assessments will
be evaluated.
� Symptom score checklist compiled on the basis of a
number of existing questionnaires for assessing
mental health and well-being in children and
parents, sexual abuse in parents’ past history, and
family problems;
� The Sexual Knowledge Picture Instrument (SKPI;
[87]) for estimating children’s sexual development
and knowledge;
� Information from police reports and indictments
considering (nature and severity of the abuse);
Public Health Services questionnaires (general
questionnaire on demographic data; parental mental
health problems such as depression; uptake of
available treatment).
Longitudinal study
Assessment instruments in the longitudinal study
(T1 and further)
Based on the type of consent that parents have given, we
will create three different categories in the sample (as-
sessment including parents only; assessment of parents
and children; and assessment of parents and children,

including biological testing). This will determine which
questionnaires, interviews, observations, and biological
tests will be used (see also Tables). All questionnaires
will be delivered to parents via a digital link and the chil-
dren full out the questionnaires at location. Interviews
with parents and/or children will be conducted at the
child and adolescent psychiatry of the AMC or, at an loca-
tion of the Public Health Services Amsterdam. If parents
prefer, interviews will be conducted at home. The primary
outcome measures will be symptoms of PTSD, dissociative
symptoms, behavioral problems, age-inappropriate sexual
behavior and knowledge, attachment disturbances, the
quality of parent–child interaction, PTSD in parents, and
parental partner relation.
Assessment instruments: questionnaires and interviews
for parents
Psychological health and well-being of the child (ques-
tionnaires and interviews administered to parents only):
� PTSD/trauma symptoms:
✓ CRIES-13, parent version (Children’s Revised
Impact of Event Scale; [88-90]): a 13-item ques-
tionnaire to screen for PTSD symptoms in children.
Internal consistency ranges from alpha 0.71 and
0.87. Convergent, divergent, and criterion validity
are good [91].
✓ DIPA (Diagnostic Infant and Preschool
Assessment; [92,93]). The DIPA is a semi-
structured interview for PTSD and other anxiety
disorders as well as mood, behavioral, reactive
attachment, and sleep disorders in children up to
age 7. The DIPA has been validated, is reliable,
and has a test-retest reliability of kappa 0.53
[92].
✓ ADIS-C (Anxiety Disorders Interview

Structured for DSMIV-child version, [94]; Dutch
version: [95]). This interview investigates PTSD
and other anxiety disorders in children aged 8 to
17 years. The ADIS-C demonstrates good to
excellent test-retest and inter-rater reliability
[96,97].
� Dissociative symptoms:
✓ CDC (Child Dissociative Checklist; [98]; Dutch
translation by [99]). The CDC is a list of 20
questions that provide indications of the presence
of dissociative symptoms in children up to age 12.
Test-retest reliability ranges from 0.57 to 0.92, and
internal consistency from alpha 0.64 and 0.95 [98].
� Attachment disturbance symptoms:
✓ AISI (Attachment Insecurity Screening
Inventory, [100]) Attachment disturbances can be
investigated with the AISI. This 20 items
questionnaire will be administered to parents with
children age 2 to 12 years.
✓ GIH (Global Indicatielijst Hechting, [101]). The
GIH is a 36 items questionnaire that investigates
attachment disturbances in children older than 12.
� Sexual behavior (and problems):
✓ CSBI (Child Sexual Behavior Inventory; [102];
Dutch translation by [103]). The CSBI is a
questionnaire to screen for symptoms of
inappropriate sexual behavior under the age of 12.
Reliability is alpha 0.93, and validity and test-retest
reliability are adequate [104].
� General psychological functioning and behavioral
problems:

✓ CBCL (Child Behavior Checklist; [105]). The
CBCL assesses internalizing and externalizing
problems in children aged 1,5 to 17 years.
Reliability ranges from alpha 0.71 to 0.89, validity
is adequate, and test-retest reliability is 0.90 [105].
� Quality of life:
✓ Kidsscreen-10, parent version [106]. Kidscreen-
10 is a 10-item questionnaire on quality of life in
children aged 8 to 17 years. Internal consistency is
alpha 0.78. [106].
Psychological health and well-being of the parent(s):
� PTSD/trauma symptoms/parental stress:
✓ IES-R (Impact of Event Scale-Revised; [107]).
The 22-item IES-R questionnaire is completed by
parents to screen for PTSD in parents. Internal
consistency ranges from alpha 0.79 to 0.90 and val-
idity from 0.53 to 0.72 [107].
✓ PERQ (Parent Emotional Reaction
Questionnaire; [108]). The 15-item PERQ is com-
pleted by parents and assesses their emotional reac-
tions to the sexual abuse of their child. Internal
consistency is alpha 0.87 and test-retest reliability
0.90 [108].
� Parental relationship:
✓ ECR (Experiences in Close Relationships;
[109]; Dutch translation and validation by [110]).
The ECR consists of 36 questions scored on a 7-
point scale, testing two dimensions of attachment in

adult partner relationships: (1) fear of rejection and
abandonment by a partner; and (2) avoidance of in-
timacy. Internal consistency ranges from alpha 0.78
to 0.93, and test-retest reliability from 0.82 to 0.89
[111].
Assessment instruments: questionnaires and interview for
the child (if consent is given)
Psychological health and well-being of the child (the fol-
lowing questionnaires and interviews will be adminis-
tered to the child, the children will have been informed
about the sexual abuse):
� PTSD/trauma symptoms:
✓ CRIES-13, child version (Children’s Revised
Impact of Event Scale; [88-90]): a 13-item
questionnaire to screen for PTSD in children aged
8 to 17 years. Internal consistency ranges from
alpha .74 to .89. The test-retest reliability
coefficient is .85 for the total score. Criterion
validity is good [112].
✓ CAPS-CA (Clinician-Administered PTSD Scale,
child and adolescent version; [113]) is a semi-
structured clinical interview for children aged 8 to
17 years that enables DSM-IV-TR PTSD diagnoses
and severity scores of posttraumatic stress
symptoms to be determined on a standardized basis.
Internal consistency is alpha 0.83; validity and
interrater reliability are good [114].
� CPTCI (Child Post-Traumatic Cognitions Inventory;
[115]). matically screens for negative thoughts that
traumatized children and adolescents, aged 8 to
18 years, might have about themselves or the world

around them. Internal consistency, test-retest
reliability, and convergent and discriminant validity
are good [115].
� Dissociative symptoms:
✓ ADES (Adolescent Dissociative Experience
Scale; [116]). The ADES is a self-completion
questionnaire that assesses dissociative symptoms
in children age 12 years and older. Reliability and
validity are good [116].
� General functioning and behavioral problems:
✓ YSR (Youth Self-Report; [105]). The YSR
assesses the behavioral and emotional functioning
of adolescents (11 years and older), including
internalizing and externalizing problems. Internal
consistency ranges from 0.55 to 0.75, validity is
good, and test-retest reliability is 0.88 [105].
� Quality of life:
✓ Kidscreen-10, child version [106]. Kidscreen-10
is a 10-item questionnaire on quality of life in
children aged 8 to 17 years. Internal consistency is
alpha 0.82 and test-retest reliability 0.55 [106].
Assessment instruments: observations child/parent
(if consent is given)
Quality of parent–child interaction (observations):
� Strange situation procedure [117,118]: During this
separation and reunion procedure, the quality of the
attachment relationship between children and their
parent is assessed.
� A 25-minute video recording will be made of three
play situations involving the child and a parent, with

degree of control varying by situation: (1) free play,
with parent following the child’s lead; (2) structured
play, with parent taking more of a lead; and (3) tidy-
ing up the toys. The video recordings will then be
coded using two coding systems: DPICS (Dyadic
Parent–child Interaction Coding System; [119]), and
EAS (Emotional Availability Scales; [120]).
Assessment instruments: biological measures
(if consent is given)
� Weight and height will be measured and body mass
index (BMI) calculated.
� The children’s growth charts were requested from
the Child Health Center.
� Genetic material (DNA) will be isolated from saliva,
after which single nucleotide polymorphisms (SNPs)
and methylation status will be determined on a
genome-wide basis. This study will examine whether
SNPs can be identified that are associated with
posttraumatic stress symptoms. We will also analyze
whether methylation status affects the degree of
symptomatology in the group of abused children
[45,46].
Qualitative study
Individual interviews will be conducted with 25 parents,
guided by the following topics: perceived condition of the
child and the family situation, experiences with health and
social services in the preceding period, experiences with
legal procedures, experiences with media attention, view-
points on the impact of child pornography, in particular on
the internet. The interviews will have an open structure.
Interviewees will be invited to tell their own story. The

subjects in the topic guide will be raised by the interviewer
if they fail to come up naturally. The interviewer will probe
for respondents’ experiences and also experiences of the
therapists who treated these children.
Outcome measures
See Tables 1, 2, and 3 for the outcome measures.
Time line and sample selection
Parents were contacted by the AMC or the Public
Health Service Amsterdam and invited to take part in
the study. Researchers will be employed who will receive
training in conducting interviews and observations, and
in scoring the observations, from the Child and Adoles-
cent Psychiatry Research Group at the AMC.
The T1 assessments took place in mid-2013, and the
data obtained will be processed, analyzed, and reported
later. In the first half of 2014, preparations will be made
for the T2 assessments. This working procedure will en-
able us to perform, process, analyze, and report on the
previous year’s assessment as well as preparing the sub-
sequent assessments.
Statistical analysis
Categorical data will be summarized as frequencies and
percentages, continuous data will be summarized by
means and standard deviations or median and interquar-
tile scores, and if appropriate Linear mixed model ana-
lysis will be used to investigate the course of the

outcomes of interest (e.g. PTSD dissociative symptoms)
and to examine and test the effects of the various child-
and abuse characteristics on the outcomes. Longitudinal
models for data assembled at T1 and further will have a
random intercept to account for individual differences at
baseline, fixed effects regression coefficients for each of
the follow-up occasions after baseline while controlling
for possible other confounding variables. The appropri-
ate covariance structure for the longitudinal models and
possible interaction effects will be assessed using log-
likelihood statistics. Growth curves will be examined by
plotting data and when appropriate we will include poly-
nomials reflecting the observed curves. Cross-sectional
Table 1 Consent for contact with parents only (questionnaires
are adult/parent versions)
Assessment
instrument
Questionnaire
or interview
Construct Standardized/
validated
Age of the
child
CRIES Questionnaire PTSD symptoms yes, in USA and in the
Netherlands
2-18 years
DIPA or ADIS-
C

Interview diagnosis and symptoms of PTSD, other anxiety
disorders, and mood,
behavioral, reactive attachment, and sleep disorders
yes, in USA and a Dutch
study in progress
2-18 years
CDC Questionnaire symptoms of dissociation yes, in USA 5-14
years
AISI or GIH Questionnaire symptoms of inhibited and
disinhibited attachment yes, in the Netherlands 2-18 years
CSBI Questionnaire symptoms of inappropriate sexual behavior
yes, in USA Dutch study
in progress
2-12 years
CBCL Questionnaire internalizing and externalizing symptoms
yes, internationally 1.5-5 years and
6-18 years
Kidscreen-10 Questionnaire quality of life yes, internationally
8-18 years
IES-R Questionnaire parental PTSD symptoms yes,
internationally parents
PERQ Questionnaire parental emotional reactions to sexual
abuse of child no parents
ECR Questionnaire attachment in adult partner relationships

yes, in USA and in the
Netherlands
parents
Table 2 Questionnaires/interviews child
Assessment
instrument
Questionnaire
or interview
Construct Standardized/
validated
Age
of
the
child
CRIES questionnaire PTSD
symptoms
yes, in USA
and in the
Netherlands
8-18
years
CAPS-CA interview PTSD diagnosis
and symptoms
yes, in USA
and in the

Netherlands
8-18
years
InADES questionnaire symptoms of
dissociation
yes, in USA
and Turkey
12-20
years
YSR questionnaire internalizing
and
externalizing
symptoms
yes,
internationally
11-18
years
CPTCI questionnaire negative
cognitions
about oneself
and the world
yes, Dutch
study in
completion
8-18
years

Kidscreen-10 questionnaire quality of life yes,
internationally
8-18
years
Table 3 Observation of parent-child play interaction
Type Construct Standardized/
validated
Age
of
the
child
Strange
situation
procedure
Observation of
child-parent
interaction
Assessment of
quality of
attachment
yes,
internationally
< 8
years
DPICS/

EAS
observation of
parent-child
play
interaction
assessment of
parenting and
quality of
interaction
yes,
internationally
< 8
years
comparisons at different time-points will also made
using linear mixed model or ordinary multivariable re-
gression analysis to examine the effects of child/parent
and abuse characteristics on the outcomes.
Confidentiality of study data
The data for this study will be collected by researchers
from the Department of Child and Adolescent Psych-
iatry at the AMC and the Department of Epidemiology
and Health Promotion, at the Public Health Service in
Amsterdam. The Clinical Research Unit of the AMC will
be asked to build and manage the database for this pro-
ject. The data will be stored in coded form by assigning

a number to each file, questionnaire, and scoring sheet.
This will prevent unauthorized persons from tracing
which file belongs to which child or parents. Study re-
sults will also be published in anonymized form.
Discussion
The ASAC-study will be the first longitudinal study to
systematically investigate signs and symptoms of sexual
abuse in infants and very young children, and on boys in
particular. These effects of the abuse will be measured at
the short-, medium-, and long-term. The effects of the
persistence of pornographic internet images, on the chil-
dren and their parents, will also be investigated. Although
CSA is common, it rarely occurs on the scale that it did in
the Amsterdam sexual abuse case, committed by one chief
perpetrator with one or two possible accomplices, and the
severity of CSA is well documented by the police. System-
atic research on the effects that CSA has on very young
children is urgently needed to better understand the psy-
chological and physical clinical presentations of such
abuse and to identify the risk- and protective factors for
psychopathology resulting from it. It is expected that CSA
has effects on the child, parents, child-interaction and par-
ental partner relation. This knowledge will enable early
recognition of problems and prompt therapeutic interven-
tion when CSA is suspected in very young children.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
RL, SB, JD, EV, AT and AV wrote the current manuscript. RL,
SB and AV are
the project leaders. AT, SB, and TB are responsible for the first
assessment in
2010. JD and EV are responsible for the assessment in 2013. All

authors read
and approved the final manuscript.
Acknowledgments
We would like to thank the following several mental health care
agencies
involved in the ASAC-study: Arkin Mental Health Care, ’t
Kabouterhuis Medical
Day Care Centre for Children, GGZ inGeest Regional Mental
Health Service
Centre, Infant Mental Health Centre IMH, KJTC Haarlem,
Slachtofferhulp, and De
Bascule Academic Centre for Child and Adolescent Psychiatry.
We would like to
acknowledge the Research Advisory Committee: Marta Santos
Pais, Anton
Bentovim, Corianne de Borgie, Corinne Dettmeijer-Vermeulen,
Danya Glaser,
Eleanore Landsmeer-Beker, Robert Lindeboom, Anthony
Mannarino, Miranda
Olff, Michael Scheeringa, Steven Tjalsma, Frederike Scheper,
Ethal Quayle, Guy
Widdershoven, and Jolien Zevalkink. We would also like to
thank Els van Meijel,
Maj Gigengack, Caroline Jonkman, and Marielle Abrahamse for
collecting
research data, and the children and parents for participating in
our study. We
would like to thank Pro Juventute and the Ministery of Security
and Justice, and
the Ministery of Health, Welfare and Sport.
Author details
1Department of Child and Adolescent Psychiatry, Academic
Medical Centre,

Amsterdam, The Netherlands. 2De Bascule, Academic Center
for Child and
Adolescent Psychiatry, Amsterdam, The Netherlands.
3Department of Social
Pediatrics, Emma Children’s Hospital, Academic Medical
Centre, Amsterdam,
The Netherlands. 4Department of Epidemiology & Health
Promotion, Public
Health Services, Amsterdam, The Netherlands. 5Department of
Child and
Adolescent Psychiatry, GGZ-InGeest/VU University Medical
Center,
Amsterdam, Netherlands. 6Department of Biological
Psychology, VU
University, Amsterdam, The Netherlands. 7Department of
Sociology and
Antropology, University of Amsterdam, Amsterdam, The
Netherlands.
Received: 29 September 2014 Accepted: 13 October 2014
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Cite this article as: Lindauer et al.: The Amsterdam Sexual
Abuse Case
(ASAC)-study in day care centers: longitudinal effects of sexual
abuse
on infants and very young children and their parents, and the
consequences of the persistence of abusive images on the
internet.
BMC Psychiatry 2014 14:295.
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AbstractBackgroundMethods/designDiscussionBackgroundProbl
em definitionResearch questions and
objectivesMethods/DesignProject organizationStudy
designSigns of sexual abuse in very young childrenLongitudinal
(cross-sequential) studyQualitative studyStudy groupsSigns of
sexual abuse in very young childrenLongitudinal study (cross-
sectional)Qualitative studyInformed

consentAssessmentsAssessment instrumentsSigns of sexual
abuse in very young childrenLongitudinal studyAssessment
instruments in the longitudinal study (T1 and
further)Assessment instruments: questionnaires and interviews
for parentsAssessment instruments: questionnaires and
interview for the child (if consent is given)Assessment
instruments: observations child/parent (if consent is
given)Assessment instruments: biological measures (if consent
is given)Qualitative studyOutcome measuresTime line and
sample selectionStatistical analysisConfidentiality of study
dataDiscussionCompeting interestsAuthors’
contributionsAcknowledgmentsAuthor detailsReferences
RESEARCH ARTICLE Open Access
Maternal post-natal tobacco use and
current parental tobacco use is associated
with higher body mass index in children
and adolescents: an international cross-
sectional study
Irene Braithwaite1*, Alistair W. Stewart2, Robert J. Hancox3,
Richard Beasley1, Rinki Murphy4, Edwin A. Mitchell5
and the ISAAC Phase Three Study Group
Abstract
Background: We investigated whether maternal smoking in the
first year of life or any current parental smoking is
associated with childhood or adolescent body mass index
(BMI).
Methods: Secondary analysis of data from a multi-centre, multi-
country, cross-sectional study (ISAAC Phase Three).

Parents/guardians of children aged 6–7 years completed
questionnaires about their children’s current height and
weight, whether their mother smoked in the first year of the
child’s life and current smoking habits of both parents.
Adolescents aged 13–14 years completed questionnaires about
their height, weight and current parental smoking
habits. A general linear mixed model was used to determine the
association between BMI and parental smoking.
Results: 77,192 children (18 countries) and 194 727 adolescents
(35 countries) were included. The BMI of children
exposed to maternal smoking during their first year of life was
0.11 kg/m2 greater than those who were not
(P = 0.0033). The BMI of children of currently smoking parents
was greater than those with non-smoking parents
(maternal smoking: +0.08 kg/m2 (P = 0.0131), paternal
smoking: +0.10 kg/m2 (P < 0.0001)). The BMI of female
adolescents exposed to maternal or paternal smoking was 0.23
kg/m2 and 0.09 kg/m2 greater respectively than
those who were not exposed (P < 0.0001). The BMI of male
adolescents was greater with maternal smoking
exposure, but not paternal smoking (0.19 kg/m2, P < 0.0001 and
0.03 kg/m2, P = 0.14 respectively).
Conclusion: Parental smoking is associated with higher BMI
values in children and adolescents. Whether this is due
to a direct effect of parental smoking or to confounding cannot
be established from this observational study.
Keywords: BMI, Tobacco use, Smoking, International, Parental
smoking, Body mass index, Child, Adolescent,
Obesity, Overweight
* Correspondence: [email protected]
1Medical Research Institute of New Zealand, Private Bag 7902,
Newtown,

Wellington 6242, New Zealand
Full list of author information is available at the end of the
article
© 2015 Braithwaite et al. Open Access This article is
distributed under the terms of the Creative Commons
Attribution 4.0
International License
(http://creativecommons.org/licenses/by/4.0/), which permits
unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate
credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were
made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to
the data made available in this article, unless otherwise stated.
Braithwaite et al. BMC Pediatrics (2015) 15:220
DOI 10.1186/s12887-015-0538-x
http://crossmark.crossref.org/dialog/?doi=10.1186/s12887-015-
0538-x&domain=pdf
mailto:[email protected]
http://creativecommons.org/licenses/by/4.0/
http://creativecommons.org/publicdomain/zero/1.0/
Background
The rising prevalence of childhood obesity is marked
[1, 2]. Concerns about the future health implications
of obesity in childhood are well documented [3, 4].
This problem has been identified in low and middle
income countries as well as affluent countries [5–7].
Potential contributors to childhood obesity are mul-
tiple and complex. Maternal smoking during pregnancy

has been identified as a risk factor for low birth weight
and small-for-gestational-age infants [8, 9] and as a likely
contributor to increased body mass index (BMI) in later
life [10, 11].
A number of mechanisms for the association between
maternal smoking in pregnancy and increased offspring
BMI have been proposed. Nicotine and carbon monox-
ide exposure have been shown to cause placental vaso-
constriction and foetal hypoxaemia, leading to low initial
birthweight. [12] Low birthweight babies have been
shown to experience rapid catch-up growth in infancy
and to have higher risk for overweight and obesity in
adolescence and adulthood [13–15]. It has been
hypothesised that in infants exposed to intra-uterine
nicotine, this phenomenon may be due to changes in the
hypothalamic-pituitary axis, affecting satiety and impulse
control [16]. Alternatively, the association between ma-
ternal smoking in pregnancy and increased offspring
BMI may be due to confounding of other lifestyle habits
of smoking parents.
Associations between higher BMIs in children and cur-
rently smoking parents have been demonstrated in previ-
ous studies [17–24] that have predominantly been limited
to small cohorts within countries. A number of these have
demonstrated an association between maternal and/or pa-
ternal smoking independently of maternal smoking before
or during pregnancy. Women who smoke during preg-
nancy have different sociodemographic and anthropomet-
ric characteristics than non-smokers and it is likely that
children who live in smoking households also have differ-
ent dietary patterns than those from non-smoking house-
holds [25]. In this study we have the opportunity to assess
the association between current parental smoking and
BMI of a large number of children and adolescents from a

range of countries, adjusting for fast food consumption.
The International Study of Asthma and Allergies in
Childhood (ISAAC) Phase Three is a multi-national
multi-centre study that has previously collected data on
heights and weights of children aged 6–7 years and 13–
14 years as well as their exposure to parental smoking at
various time points in their lives. Although originally de-
signed to measure time trends in the prevalence and se-
verity of asthma, rhinoconjunctivitis and eczema and to
explore the relationship between lifestyle, other putative
risk factors and the development of asthma and allergies
[26], it has provided us with the opportunity to explore
the relationship between lifestyle or environmental fac-
tors, such as parental smoking, and BMI.
In ISAAC Phase Three information on parental smok-
ing was gathered through an environmental question-
naire (EQ) that was optional for parents of children and
adolescents themselves to answer. The EQ also asked for
information on fast food consumption of participants,
which we took into account as a confounding variable
given the sociodemographic patterning of unhealthy life-
styles [25].
Here we present analyses of exposure to environmen-
tal tobacco exposure and BMI of children (aged 6 to
7 years) and adolescents (aged 13 to 14 years). We
hypothesised that maternal smoking in the first year of
life would be associated with a greater BMI in children,
and that there would be a similar association between
current maternal and/or paternal smoking and BMI of
children and adolescents.
Methods

This study is a secondary analysis of the data gath-
ered during the ISAAC Phase Three study. Permission
was granted by the ISAAC Steering Committee to ac-
cess the data. ISAAC is a multicentre, multi-country,
multiphase, cross-sectional study investigating the
prevalence of the symptoms of asthma, rhinoconjunc-
tivitis and eczema, and the role of risk factors, as pre-
viously described [26]. ISAAC Phase Three included
116 sites that had originally participated in ISAAC
Phase One and 168 sites that were new to Phase
Three. A minimum of 10 schools were randomly
sampled within pre-defined geographic areas (centres).
Participants (13–14 year olds and 6–7 year olds) were
selected from within those schools depending on the
local situation; either the grade, level or year where
classes with the most children in the age ranges were
selected, or by age group, where only children within
that age group, regardless of grade, level or year were
selected. ISAAC Phase Three used the Phase One
standardised core questionnaire on symptoms of
asthma, rhinoconjunctivitis and eczema, and included
an optional environmental questionnaire (EQ) to col-
lect potential risk factor data including height, weight,
and parental smoking. The EQ was developed by the
ISAAC steering committee to assess potential risk fac-
tors for the development of asthma in children that
had been identified in previous research. Where pos-
sible, questions previously published in the literature
were replicated in the EQ, otherwise the questions
were developed by the ISAAC steering committee.
The EQ was piloted in New Zealand, Latin America,
French Speaking Africa and the Asia-Pacific regions
and was optional for all participating centres. Instruc-
tions were provided in the event centres wished to
Braithwaite et al. BMC Pediatrics (2015) 15:220 Page 2 of 8

translate it into the local language. Adolescents self-
completed their questionnaires while at school and
children were sent home with questionnaires for their
parents or guardians to complete. A participation rate
of 90 % was targeted. Where participation rates were
below 90 % for adolescents, a second visit was carried
out to include those that were absent when the EQ
was originally answered. The EQ was issued a num-
ber of times to parents of the 6–7 year olds in case
the children were away from school due to ill health.
The questionnaires are on the ISAAC website [27].
Main outcome variable - body mass index
Height and weight were reported by the parents of the
children, and were self-reported by adolescents. In some
centres, each subject’s height and weight were measured
objectively; there were no standardised or specific in-
structions for doing this. BMI was calculated (weight
(kg)/height (m)2). We subsequently adjusted for whether
heights and weights were measured or reported in each
centre.
Explanatory variables
Parental smoking of study participants was assessed
using the following questions:
For children:
1. Does your child’s mother (or female guardian)
smoke cigarettes?
a. If yes, how many cigarettes does the child’s
mother (or female guardian) smoke each day?
2. Does your child’s father (or male guardian) smoke

cigarettes?
a. If yes, about how many cigarettes does the child’s
father (or male guardian) smoke each day?
3. Did your child’s mother (or female guardian) smoke
cigarettes during your child’s first year of life?
For adolescents:
1. Does your mother (or female guardian) smoke
cigarettes?
2. Does your father (or male guardian) smoke
cigarettes?
Each explanatory variable was examined separately for
both age groups. To assess the presence of a dose–re-
sponse relationship in the children, the number of ciga-
rettes smoked per day by the parents were categorised
for the purpose of analysis as 0, 1–9, 10–19, 20–29, and
30 or more.
Fast food consumption was assessed by parents of
children and adolescents reporting their weekly con-
sumption of ‘fast food’/‘burgers’ over the previous
12 months, categorised in the questionnaire as’never or
occasionally’, ‘once or twice per week’, and ‘three or more
times per week’.
Country GNI was based on the 2006 World Bank of
Gross National Income by country. The World Bank
categories of high-, high middle-, low middle-, and low-
income countries were dichotomised into high income

(high- plus high middle-income) and low income (low
middle- plus low-income) categories.
Participants
For the children, data which included heights, weights
and parental smoking variables were submitted from 73
centres in 32 countries (214 706 subjects). For the ado-
lescents, data were submitted from 122 centres in 53
countries (362 091 subjects).
Centres that provided >70 % data for current maternal
smoking were included in our analyses. Some of these
centres did not gather data on current paternal smoking
or in the case of children, maternal smoking in the first
year of life. Individuals without complete age, sex, fast
food consumption, height or weight data were excluded.
Data cleaning
To preserve as much BMI data as possible, but also to
eliminate likely erroneous data, we applied the following
thresholds:
– For children in each centre, those in the top and
bottom 0.5 % of weights and heights (n = 1,391), and
those with heights less than 1.0 metre were
excluded (n = 346). Children with BMI less than
9 kg/m2 and greater than 40 kg/m2 were excluded
(n = 215).
– For adolescents in each centre, those in the top and
bottom 0.5 % of weights and heights (n = 3,712), and
those with heights less than 1.25 m were excluded
(n = 904). Adolescents with BMI less than 10 kg/m2
and greater than 45 kg/m2 were excluded (n = 360).

Following sequential application of the exclusion and
data cleaning criteria described above, 77 192 children
(31 centres/18 countries) and 194 727 adolescents (72
centres/35 countries) were included in the final analysis
(Fig. 1). 147 274 adolescents from 55 centres provided
self-reported height and weight while 47 453 adolescents
from 17 centres provided measured heights and weights
(Additional file 1: Figure S1).
Statistical analysis
BMI was assessed separately for each age group using a
general linear mixed model with centre as a random ef-
fect and GNI for each country, the individual’s age, sex,
measurement type, fast food consumption, and each
F1
parental smoking variable as fixed effects. The BMI
values reported are the modelled means for those who
had no exposure to either parent smoking for all ages in
the children and adolescent’s groups respectively.
Because of an interaction found between paternal
smoking and GNI, separate estimates were made for pa-
ternal smoking at each GNI level for both children and
adolescents. Further analyses were undertaken separately
for male and female adolescents and those whose
heights and weights were objectively measured due to
interactions found between sex and current maternal
smoking, sex and current paternal smoking, measure-
ment type and current maternal smoking, and measure-
ment type and current paternal smoking.

Results
For the children, the basic characteristics of each centre
are shown in Additional file 2: Table S1, and for the ado-
lescents, basic characteristics are shown in Additional
file 3: Table S2.
Exposure to parental smoking
In the children, 9.9 % had been exposed to maternal
smoking in their first year of life (Additional file 4:
Figure S2a). 43.1 % of children were exposed to some
kind of current parental smoking (10.4 % both parents,
4.6 % maternal smoking only and 28.1 % paternal smok-
ing only) (Additional file 4: Figure S2b).
44.4 % of adolescents reported exposure to current
parental smoking (12.4 % to both parents, 6.9 % to ma-
ternal smoking only, and 25.2 % to paternal smoking
only) (Additional file 4: Figure S2c).
Exposure to parental smoking and BMI
In both age groups GNI and fast food variables showed
a significant association with BMI but did not have any
influence on the smoking-BMI associations.
Children
Figure 1a shows the difference in BMI (kg/m2) between
children not exposed to parental smoking at any time
point and those exposed to maternal smoking in the first
year of life, current maternal smoking and current pater-
nal smoking in each centre, with countries grouped into
high and low GNI categories .
There were no interactions between any maternal
smoking variables, current paternal smoking, measure-
ment type, sex or age. Because of a significant inter-

action found between GNI and paternal smoking,
estimates are given for paternal smoking by GNI
category.
The estimated mean BMIs in children not exposed to
parental smoking at all were 14.4 and 14.7 kg/m2 for
ages 6 and 7 respectively. After controlling for country
GNI, centre, individual fast food usage, age and meas-
urement type, there was an association between expos-
ure to parental smoking at any time and BMI (Table 1).
In high GNI countries children of smoking fathers had
larger BMIs, than those with non-smoking fathers, while
in low GNI countries children of smoking fathers had
smaller BMIs than those of non-smoking fathers
(Table 1).
There was a dose response relationship between the
number of cigarettes smoked daily by each parent and
the BMI of the child (Table 2).
Adolescents
Figure 1b shows the difference in BMI (kg/m2) between
adolescents with no exposure to current parental smok-
ing and those with current maternal or paternal smoking
in each centre.
Because of significant interactions found between sex
and maternal smoking, sex and paternal smoking, meas-
urement type and both maternal and paternal smoking,
analyses were done separately for each sex, and then
using measured height and weight data only. There was
also an interaction between GNI and paternal smoking,
so estimates are given for paternal smoking by GNI.
Fig. 1 The association between parental smoking and BMI of
study

subjects. The percentage of subjects exposed to each smoking
variable is shown in parentheses after each country. Solid dots
represent centres where height and weight were reported by
parents, circled dots represent centres where height and weight
were measured objectively. (a) shows the association between
children’s BMI and; maternal smoking in the first year of life in
the
top graph, current maternal smoking in the middle graph, and
current paternal smoking in the bottom graph. (b) shows the
association between adolescent’s BMI and; current maternal
smoking
in the top graph and current paternal smoking in the bottom
graph
Table 1 Association between parental smoking and BMI of
study participants (+/− kg/m2, (SE) and P value)
No exposure to parental smoking Mother smoked 1st
year of life
Mother currently
smokes
Father currently smokes Father currently smokes
High GNI countries Low GNI countries
Children (N = 77 192) 14.66a +0.11 (0.04) P = 0.002 +0.07
(0.03) P = 0.03 +0.15 (0.02) P < 0.0001 −0.14 (0.05) P = 0.004
Adolescent Females (N = 98 238) 19.72a N/A +0.22 (0.03) P <
0.0001 +0.18 (0.03) P < 0.0001 −0.05 (0.04) P = 0.17
Adolescent Males (N = 96 489) 19.78a N/A +0.18 (0.03) P <
0.0001 +0.06 (0.03) P = 0.04 −0.03 (0.04) P = 0.48
aEstimated BMIs for boys aged 7 years and adolescents aged 14

years. Associations stated are additive
Data were available for 98 238 females. For those not
exposed to parental smoking, estimated mean BMIs
were 19.32 and 19.72 kg/m2 for ages 13 and 14 respect-
ively. After controlling for country GNI, centre, individ-
ual fast food consumption, age and measurement type,
there was an association between BMI and both mater-
nal (+0.23 kg/m2) and paternal (High GNI +0.18 kg/m2
and Low GNI −0.05 kg/m2) smoking (Table 1).
When analyses were restricted to those adolescent fe-
males who had measured height and weight data (N = 25
675), there still appeared to be a tendency towards a
higher BMI with maternal smoking, (+0.11 kg/m2: SE
0.06, P = 0.06), but no association between paternal
smoking and BMI (−0.03 kg/m2: SE 0.05, P = 0.54).
Data were available for 96 489 males. For those not ex-
posed to parental smoking, the estimated mean BMIs
were 19.51 and 19.78 kg/m2 for ages 13, and 14 respect-
ively. After controlling for country GNI, centre, individ-
ual fast food consumption, age and measurement type,
there was an association between BMI and maternal
smoking (0.19 kg/m2), but not paternal smoking
(Table 1).
When analysis was restricted to those adolescent
males that supplied measured height and weight data
(N = 21 778) there was no significant association be-
tween maternal or paternal smoking and BMI (mater-
nal smoking: (−0.02 kg/m2: SE 0.06, P = 0.80), paternal

smoking: (−0.01 kg/m2: SE 0.05, P = 0.82)).
Discussion
In this study which included populations with wide vari-
ation in the social patterning of smoking, we have demon-
strated an association between maternal smoking in the
first year of life and a greater BMI in children by the age 6–
7 years. We have also shown independent but additive asso-
ciations between current maternal or paternal smoking and
children’s BMI at age 6–7. Children whose mother smoked
in their first year of life and who had both parents currently
smoking had BMIs that were on average 0.29 kg/m2 greater
than children who had no exposure to parental smoking at
all. We also found a dose–response between the number of
cigarettes smoked daily by each parent and the BMI of the
child. In adolescents we found adolescent females had a lar-
ger BMI if their mother or father smoked, and males had a
larger BMI if their mothers smoked.
Our findings in children are consistent with those of
Raum et al. who found a greater BMI at the age of 6 in
offspring of mothers who smoked both in the first year of
life and currently, independent of maternal smoking be-
fore or during pregnancy [17]. Kaufman-Shriqui and col-
leagues [28] reported an association between current
maternal smoking and overweight or obesity in a small
sample of lower socioeconomic Israeli children aged 4 to
7 years. Florath and colleagues [23] demonstrated a sig-
nificant association between current maternal smoking
and the BMI of 8 year old German children, and a slightly
larger association between paternal smoking and BMI in
the same sample. Conversely, Toschke and colleagues [29]
evaluated associations between maternal smoking patterns
pre- and post-pregnancy and the BMI of children aged
from 5 to 7 years. They found an association between ma-

ternal smoking in pregnancy and obesity in children, but
no association with smoking after pregnancy, concluding
that intrauterine exposure to tobacco smoking was instru-
mental in the association. In a study from Japan, Oyama
and colleagues [30] also concluded that while smoking
during pregnancy was independently associated with rapid
weight gain between one and 18 months of age, but daily
current smoking by the mother was not.
We did not have any data available on maternal smok-
ing during pregnancy, so were not able to test whether
the associations between childhood BMI and current
parental smoking in our sample were independent of
this variable. It is likely that maternal smoking in the
first year of an infant’s life is associated with maternal
smoking during pregnancy and some of the association
between maternal smoking in the first year of life and
the child’s BMI may be explained in this way. However,
the independent association and dose response effect we
have seen between current maternal and paternal smok-
ing and BMI of children at the age of 6 years supports
causal inference.
In our assessment of adolescent data, the association be-
tween current parental smoking and BMI was less clear.
There was a greater BMI in adolescent females with either
parent smoking, but adolescent males had a greater BMI
when their mother smoked, not when their father smoked.
When analysis was restricted to adolescents that supplied
measured heights and weights only, the effect sizes were
smaller and not statistically significant. Few studies have
previously explored this association. Associations between
parental smoking and BMI have been demonstrated in Tai-
wanese 9 to 14 year olds by Chen and colleagues [31], and
in Israel Huerta et al [24] have shown that parental

Table 2 Association between the number of cigarettes smoked
daily by parents and BMI of the children, compared to BMI of
children whose parents do not smoke (+/− kg/m2, (SE) and P
value
Number of cigarettes smoked daily None 1–9 10–19 20–29 30+
Maternal P < 0.0001 - +0.04 kg/m2 (0.04) +0.20 kg/m2 (0.04)
+0.35 kg/m2 (0.05) +0.51 kg/m2 (0.14)
Paternal P < 0.0001 - +0.06 kg/m2 (0.03) +0.13 kg/m2 (0.03)
+0.19 kg/m2 (0.03) +0.34 kg/m2 (0.06)
smoking is an independent risk factor for overweight and
severe overweight in 8–13 year old offspring, and that there
was a dose–response relationship between the number of
parental smokers and the risk of overweight. The estimated
effect on BMI in our sample was small at an individual level
(additive effect of up to 0.29 kg/m2 in children, 0.18 kg/m2
and 0.22 kg/m2 in male and female adolescents respect-
ively). However, given the long term consequences of child-
hood overweight and obesity, even a small change in the
mean BMI within a population could be of major public
health significance.
This study has also shown that a large proportion of chil-
dren and adolescents report parental cigarette smoking des-
pite its well-known associations with childhood illnesses.
Current maternal smoking was reported in 15 % and 20 %
of children and adolescents respectively. 39 % of children
and 38 % adolescents in our sample reported current pater-

nal smoking. Given that paternal smoking was independ-
ently associated with an increased BMI in children, the
high proportion of children potentially exposed to paternal
smoking is of concern. Our finding that children and ado-
lescents of smoking fathers in high GNI countries had lar-
ger BMIs than those of non-smoking fathers might be
consistent with the observation that both smoking behav-
iours and obesity have tended to become more concen-
trated in lower socioeconomic groups within high GNI
countries [32, 33], although we did not have each individ-
uals’ socioeconomic information to confirm this theory.
The lower BMI found in children of smoking fathers in low
GNI countries is more difficult to explain, but with only a
small number of centres and participants contributing to
the analysis, this result may be spurious.
Because of the observational nature of this study, we
cannot determine that parental smoking is the cause of
an elevated BMI. It is possible that smoking may be a
marker of other factors that influence BMI such as so-
cioeconomic status, dietary factors, maternal smoking
during pregnancy, physical activity or inactivity or
whether the adolescents themselves smoked cigarettes.
Of these possible confounders, we were able to adjust
for fast food as a marker of obesogenic dietary habits
which did not alter the associations.
The mechanisms for an association between childhood
exposure to parental smoking and BMI are not yet identi-
fied. It is possible that parental smoking is reflective of an
unhealthy lifestyle associated with other factors that lead to
an increase in childhood BMI [30, 34], or possibly parents
may smoke with the perception that this is helping to con-
trol their own weight, and so are less vigilant about family
diet. The weaker association between BMI and parental
smoking in adolescence may reflect increasing independ-

ence of the adolescent from the household, thus they are
less exposed to parental smoking and associated lifestyle
factors.
Strengths and limitations
The major strengths of this study are its size and multi-
centre structure, with 194 727 adolescents from 35
countries and 77 192 children from 18 countries. Many
of the centres were from middle and low income coun-
tries from which data on the association between paren-
tal smoking and BMI have not previously been reported.
The main limitation to this study is the observational
design which allows identification of associations, but
not of temporal sequence or causality. The assessments
were undertaken by questionnaire leading to errors in
the parent-reported weights of their children and self-
reported weights of the adolescents. Parents may also
have misreported their own smoking levels. Such mis-
classifications are likely to have reduced any effect to-
wards a null hypothesis. For centres that objectively
measured heights and weights, there were no standar-
dised instructions for doing this.
ISAAC comprised a self-selected group of centres
without intent to represent any population. The subset
of ISAAC Centres that then decided to utilise the Envir-
onmental Questionnaire is also a self-selected group.
This paper outlines the findings only in the sample that
participated in the study, thus there is the possibility that
these results are not representative of the population.
Although we were able to adjust the analysis for GNI,
centre, and each subjects’ fast food consumption, BMI
measurement type, and sex in our analysis, we have no
data on maternal smoking during pregnancy, individual
socioeconomic status, parental BMI, or whether adoles-

cents themselves smoked, all potentially affecting young
peoples’ BMI [28, 31, 35].
Conclusions
This study has demonstrated an association between ex-
posure to maternal smoking in the first year of life and
greater BMIs of 6–7 year old children and that current
maternal or paternal smoking may pose a risk of similar
magnitude, with a dose response effect. Exposure to
current maternal or paternal smoking is associated with
greater BMIs in adolescent females, while only maternal
smoking is associated with greater BMIs in adolescent
males. As for all observational studies, causality cannot
be proven, but the findings raise the possibility that
current parental smoking may contribute to overweight
and obesity in childhood.
Additional files
Additional file 1: Figure S1. Flow of subjects through study.
Children
are represented in panel (a) and adolescents in panel (b). (TIFF
3798 kb)
Additional file 2: Table S1. basic characteristics of contributing
centres
for 6–7 year old children, including association between
parental
dx.doi.org/10.1186/s12887-015-0538-x
dx.doi.org/10.1186/s12887-015-0538-x
smoking and BMI (+/- kg/m2, (SE)) of participants in each

centre.
(DOC 73 kb)
Additional file 3: Table S2. basic characteristics of contributing
centres
for adolescents, including association between parental smoking
and BMI
(+/- kg/m2, (SE)) of participants in each centre. (DOC 122 kb)
Additional file 4: Figure S2. Reported exposure of study
subjects to
parental smoking. Panel (a) shows the proportion of 6–7 year
olds
exposed maternal smoking in their first year of life, panel (b)
shows the
proportion of 6–7 year olds exposed to any current parental
smoking,
and panel (c) shows the proportion of adolescents exposed to
any
current parental smokingii. (TIFF 8254 kb)
Competing interests
All authors declare that they have no conflicts of interest
relating to the
development of this article.
Authors’ contributions
All authors agreed the study design. The data was gathered by
the ISAAC
Study Group during ISAAC Phase Three. EM acquired funding.
AWS
undertook the statistical analysis. IB drafted the manuscript. All
authors
reviewed and revised the manuscript for important intellectual
content. All
authors have read and reviewed the manuscript and have given

approval for
the manuscript to be submitted.
Acknowledgements
Correspondence: Irene Braithwaite, MBCHB, Medical Research
Institute of
New Zealand, Private Bag 7902, Wellington 6242, New Zealand
Author guarantee: Mr A Stewart and Dr I Braithwaite had
access to all the
data on the study and take responsibility for the integrity of the
data and
accuracy of the data analysis.
Funding
This work was supported by Cure Kids New Zealand through a
grant to
Professor E Mitchell and Dr I Braithwaite. Cure Kids New
Zealand had no role
or influence in design and conduct of the study; collection,
management,
analysis, and interpretation of the data; and preparation, review,
or approval
of the manuscript; and decision to submit the manuscript for
publication.
ISAAC Phase Three: We are grateful to the children and parents
who
participated in the ISAAC Phase Three Study. We are also
grateful to the
ISAAC Steering Committee, the ISAAC International Data
Centre and ISAAC
Phase Three Principal Investigators and Regional and National
coordinators
as listed below.
ISAAC Steering Committee:N Aït-Khaled* (International Union
Against
Tuberculosis and Lung Diseases, Paris, France); HR Anderson

(Division of
Community Health Sciences, St Georges, University of London,
London, UK);
MI Asher (Department of Paediatrics: Child and Youth Health,
Faculty of
Medical and Health Sciences, The University of Auckland, New
Zealand); R
Beasley* (Medical Research Institute of New Zealand,
Wellington, New
Zealand); B Björkstén* (Institute of Environmental Medicine,
Karolinska
Institutet, Stockholm, Sweden); B Brunekreef (Institute of Risk
Assessment
Science, Universiteit Utrecht, Netherlands); J Crane
(Wellington Asthma
Research Group, Wellington School of Medicine, New Zealand);
P Ellwood
(Department of Paediatrics: Child and Youth Health, Faculty of
Medical and
Health Sciences, The University of Auckland, New Zealand); C
Flohr
(Department of Paediatric Allergy and Dermatology, St Johns
Institute of
dermatology, St Thomas’ Hospital, London, UK); S Foliaki*
(Centre for Public
Health Research, Massey University, Wellington, New
Zealand); F Forastiere
(Department of Epidemiology, Local Health authority Rome,
Italy); L García-
Marcos (Respiratory Medicine and Allergy Units, ‘Virgen de la
Arrixaca’
University Children’s Hospital, University of Murcia, Spain); U
Keil* (Institut für
Epidemiologie und Sozialmedizin, Universität Münster,
Germany); CKW Lai*
(Department of Medicine and Therapeutics, The Chinese

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