This study aimed to estimate the lifetime prevalence of Gilles de la Tourette's syndrome (GTS) in adolescents aged 16-17 in Israel. Over 28,000 adolescents were screened using a 4-item questionnaire followed by examination by a psychiatrist. 12 individuals met diagnostic criteria for GTS, yielding a point prevalence of 4.3 per 10,000. Rates of obsessive-compulsive disorder (OCD) were higher in those with GTS (41.7%) compared to the general population (3.4%), but rates of attention deficit hyperactivity disorder were similar. This study provides prevalence estimates for GTS in line with previous studies and highlights the high comorbidity between GTS and OCD.

1. An Epidemiologic Study of Gilles de la Tourette's
Syndrome in Israel
Alan Apter, MD; David L. Pauls, PhD; Avi Bleich, MD; Ada H. Zohar, PhD; Shmuel Kron, MD; Gidi Ratzoni, MD;
Anat Dycian, MA; Moshe Kotler, MD; Avi Weizman, MD; Natan Gadot, MD; Donald J. Cohen, MD
Objectives: The goal of this study was to estimate the
lifetime prevalence of Gilles de la Tourette's syndrome
(GTS) in adolescents aged 16 to 17 years.
Design: Population-based epidemiologic study.
Subjects: Eighteen thousand three hundred sixty-four
males and 9673 females aged 16 to 17 years screened for
induction into the Israel Defense Force.
Results: Of the 28 037 individuals screened, 12 met diag-
nostic criteria for GTS. The point prevalence in this popu-
lation was 4.3m=+-1.2(meanm=+-SE)per 10 000. The 95% con-
fidence interval for this estimate is 1.9 to 6.7 per 10 000. The
point prevalencewas 4.9m=+-1.6 per 10 000 for males (95% con-
fidence interval, 1.8 per 10 000) and 3.1 m=+-1.8per 10 000 for
females (95% confidence interval, 0 to 6.6 per 10 000). The
rate ofobsessive-compulsivedisorder (OCD) was significantly
elevated amongthe subjects with GTS (41.7%) comparedwith
the population point prevalence of OCD (3.4) in those with-
out GTS. In contrast, the rate ofattention deficit hyperactivity
disorder was only 8.3% comparedwith the populationpoint
prevalence of 3.9% in those individuals without GTS.
Conclusions: The prevalence estimates from this pop-
ulation-based study are in agreement with previous re-
sults based on surveys of younger children. The sex ratio
observed in this study is not as large as reported in Pre-
vious studies and remains to be explored in other studies
of adolescents and adults.
(Arch Gen Psychiatry. 1993;50:734-738)
Gilles
DE LA Tourette's syn¬
drome (GTS) is a neu¬
ropsychiatrie disorder
with onset in childhood,
characterized by motor
and phonic tics that wax and wane over
the course of the illness. During the past
decade, GTS has been the focus of con¬
siderable research1·2; however, few epide¬
miologie studies have been conducted to
establish the prevalence of GTS in the gen¬
eral population. In an early study, Lucas
and colleagues3 searched for all cases of GTS
in a computerized diagnostic index main¬
tained at the Mayo Clinic, Rochester, Minn.
Twenty-seven patients were identified from
this registry; however, not all came from
the immediate Rochester area. To obtain a
better prevalence estimate, Lucas and col¬
leagues attempted to ascertain all cases iden¬
tified between 1968 and 1979 in Roches¬
ter. Three individuals were located, yielding
a rate for this community of 0.046 per
10 000.
A more recent study surveyed all phy¬
sicians in the state of North Dakota in an
attempt to identify all patients with GTS
in their care.4 The prevalence estimate for
this study was considerably higher than that
reported by Lucas and coworkers.3 For
adults, the total overall rate was 0.50 per
10 000. The prevalence was estimated to
be 0.77 per 10 000 for males and 0.22 per
10 000 for females. Among school-age chil¬
dren, the total rate was estimated to be 5.2
per 10 000, with a prevalence of 9.3 per
10 000 for males and a prevalence of 1.0
per 10 000 for females.
A shortcoming of both of these stud¬
ies was the reliance on identified treated
cases. To address this problem, a study of
From the Geha Psychiatric
Hospital, Department of Child
and Adolescent Psychiatry,
Sackler School of Medicine, Tel
Aviv University, Petah Tikva,
Israel (Drs Apter, Ratzoni,
Weizman, and Gadot); the
Department of Psychiatry,
Sakler School of Medicine, Tel
Aviv University, Ramat Aviv,
Israel (Drs Apter, Bleich, and
Ratzoni); Israel Defense Force
(Drs Apter, Bleich, Kron, and
Ratzoni and Ms Dycian); the
Child Study Center (Drs Pauls,
Zohar, and Cohen) and the
Department of Genetics
(Dr Pauls), Yale University
School of Medicine, New Haven,
Conn; the Department of
Psychology, Hebrew University,
Jerusalem, Israel (Dr Zohar);
and the Department of
Psychiatry, Albert Einstein
College of Medicine, New York,
NY (Dr Kotler).
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2. SUBJECTS AND METHODS
SAMPLE
The sample consisted of a cohort of 16- to 17-year-old Is¬
raelis screened at an Israel Defense Force induction center
in Israel. Some institutionalized individuals (0.02%) were
not personally evaluated, but extensive information about
them was available from medical records. All medical records
from institutionalized adolescents were evaluated by three
board-certified child psychiatrists (A.A., G.R., and A.W.) to
determine whether any of them met criteria for GTS; no
individuals with GTS were identified. Females who claimed
exemption from the military on religious grounds (on av¬
erage, 5% of the general Israeli population) were not in¬
cluded in the study.
All subjects were screened for lifetime occurrence of
motor and/or phonic tics at the time of preliminary induc¬
tion evaluations. Altogether, more than 28 000 individuals
were assessed during a 1-year period.
ASSESSMENT PROCEDURE
A three-stage ascertainment procedure was used to identify
affected individuals. The initial screeningstage utilized a four-
item self-report questionnaire (Table I ) that elicited infor¬
mation about the lifetime occurrence of tics. After comple¬
tion of the questionnaire, each subject was examined by an
induction center physician who was trained to recognize tics
and GTS. Altogether, 12 psychiatrists participated in the first-
stage screening. All of them were trained by a board-certified
child psychiatrist experienced with GTS (A.W.). The train¬
ingincluded lectures and audio-visual materials obtained from
the GTS clinic at the Yale University Child Study Center, New
Haven, Conn. All 12 Israel Defense Force clinicians specif¬
ically asked the same four questions, reviewed the written
responses, and observed the young people to assess the pres¬
ence of tics. For quality assurance, each physician signed the
questionnaire after the physical examination. All individuals
who responded positively to at least one screening question
were included in the second stage of the evaluation.
In the second stage of ascertainment, all individuals
were examined clinicallyby one of three board-certified child
psychiatrists (A.A., G.R., and A.W.) with special research
interest and training for the diagnosis of tic disorders. The
second stage of the assessment consisted of a nonstructured
clinical interview that assessed general psychopathology and
determined the nature of tics, if present, and the course of
the tic disorder. If, after this interview, the clinician be¬
lieved that the individual possibly met DSM-III-R criteria
for GTS, the adolescent was included in the third stage of
the ascertainment process.
In the third stage, individuals were formally adminis¬
tered the Yale Schedule for Tourette's Syndrome and Other
Behavioral Syndromes (YSTSOBS)7 by a member of the same
team of child psychiatrists that conducted the second-stage
interviews. The YSTSOBS is a precoded structured inter¬
view developed specifically for a family study of GTS.8 The
tic section of this interview grew out of a questionnaire first
developed for a survey designed to collect information about
the presence and severity of tic symptoms from the mem¬
bership of the Tourette Syndrome Association.9 The most
informative and reliable items from that questionnaire
were combined with items from rating scales developed
for clinical assessment of GTS and related disorders.10
The OCD section of the interview was developed from
items included in the Yale-Brown Obsessive Compulsive
Scale.11 Specifically, items that elicit information regard¬
ing the presence of obsessions and compulsions, the
senselessness or repugnance of those symptoms, and
resistance to the thoughts and behaviors are included.
Furthermore, the YSTSOBS includes the Schedule for Af¬
fective Disorders and Schizophrenia for School-age Chil¬
dren,12 which enabled assessment of any psychiatric dis¬
order during the adolescent's lifetime.
To determine the sensitivity and specificity of the four-
item screening instrument, 562 consecutive individuals who
completed the four-item screening instrument were inter¬
viewed by trained child psychiatrists (G.R. and A.A.) who
were "blind" to the responses on the screening question¬
naire. The interviewers completed the sections of the
YSTSOBS that elicited information necessary for diagnoses
of GTS and tics, OCD, and ADHD.
school-age children was conducted in Monroe County,
New York.3 In this study, individuals were identified through
referrals resulting from public announcements, contact with
the public and private schools, and mailings to physi¬
cians and other treating health care professionals. Chil¬
dren who were identified through this screening were thor¬
oughly evaluated by the team of researchers using a battery
of standard instruments. With use of this two-stage as¬
certainment scheme, the population prevalence was es¬
timated to be 2.9 per 10 000.
In the most recent study,6 selected classrooms in a
southern California school district were surveyed. A
child study team that consisted of a psychologist, a
nurse, a speech and language specialist, a principal,
and teachers received student referrals from teachers
and parents for psychoeducational assessments. During
these interactions with the children, the school psy¬
chologist observed children for motor and vocal tics.
Children were referred from among more than 3000
students in three schools during a period of 2 years.
The sample included an overrepresentation of full-day
special education classes. Prevalence rates were esti¬
mated correcting for the number of special classes and
including individuals who met criteria for GTS, except
that the symptoms had not been present for 1 year.
The frequency of GTS was reported to be 105.3 per
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3. 10 000 for males and 13.2 per 10 000 for females.
While the Monroe County5 and southern California6
studies obtained cases from sources other than physi¬
cians, neither conducted a general population screen¬
ing for tics. Thus, to our knowledge, no study has sys¬
tematically screened all individuals in a population for
tics who were then followed up with a systematic clin¬
ical evaluation for the presence of GTS.
Israel provides a unique opportunity for population-
based studies of developmental psychopathology in ad¬
olescence. Between the ages of 16 and 17 years, all
Jewish and Druze adolescents are evaluated for physi¬
cal, psychological, and cognitive fitness in preparation
for army service. The only exceptions are some reli¬
gious girls. Furthermore, because individuals can be
observed closely throughout their military service and
because males who serve in the reserves can be fol¬
lowed up for many years, there is an opportunity to
learn more about the course of the disorder identified
in a population survey.
We took advantage of this complete population screen¬
ing in Israel. Approximately 28 000 adolescents between
the ages of 16 and 17 years who were being screened for
military induction were also screened for the presence of
tics. Our goals were to estimate (1) the point prevalence
of GTS, (2) the role ofobsessive-compulsive disorder (OCD),
and (3) attention-deficit hyperactivity disorder (ADHD)
among the individuals with GTS identified from a large
unselected population-based sample.
The cohort of individuals with GTS identified in this
initial screening are being followed through the course of
their military experience to determine the effect of stress
on the manifestation of the disorder. Gilles de la Tourette's
syndrome is a well-defined neuropsychiatrie entity with
important implications for the study of child and ado¬
lescent development and lends itself to a developmental
epidemiologie approach. Such a study of GTS could pro¬
vide a model for the study of similar psychopathologic
conditions as they develop through adolescence into
adulthood.
RESULTS
A total of 18 364 males and 9673 females between the
ages of 16 and 17 years were screened. The disparity in
the number of males and females reflects the fact that this
induction center specializes in the induction of males. Thus,
there are normally more males than females seen for screen¬
ing at this location. The only selection criterion is gender;
thus, the prevalence estimates should not be affected ex¬
cept that the estimate for females will have a larger SE.
Nine males and three females were diagnosed as hav¬
ing GTS. The point prevalence was 4.9±1.6 (mean±SE)
per 10000 for males and 3.1±1.8 per 10000 for fe¬
males. The 95% confidence intervals were 1.8 to 8.0 and
0 to 6.6 per 10 000 for males and females, respectively.
The overall point prevalence in this sample was 4.3 ± 1.2
per 10 000 (95% confidence interval, 1.9 to 6.7 per 10 000).
The male-to-female ratio was approximately 1.6:1.
The disorders associated with GTS are shown in
Table 2. Five (41.7%) of the 12 individuals had OCD;
only one (8.3%) had ADHD. The individual with ADHD
also had OCD and a wide range of other behavioral
problems.
Ofthe 562 individuals included in the sensitivity study,
11 were diagnosed as having a tic disorder. Of these 11
individuals, one met criteria for GTS and 10 had chronic
tics. Only one of these 11 denied having tics during the
initial screening. Thus, the sensitivity of the initial screen¬
ing instrument to identify tics was excellent (0.91); how¬
ever, the specificity was quite low. Of the 562 individuals
in this substudy, 62 answered positively to one of the
items on the screening instrument. As indicated above,
only 10 of those 62 actually met criteria for either chronic
tics or GTS. An additional four individuals met criteria
for transient tic disorder. While the specificity of this screen¬
ing method is low, for the purposes of our study, it was
critical to have the sensitivity of the screening instrument
as high as possible so as not to miss any affected indi¬
viduals. No individual who denied having tics on the screen¬
ing questionnaire was determined to have GTS.
As indicated above, all 562 individuals were inter¬
viewed to assess the lifetime occurrence of OCD and ADHD.
As seen in Table 1, the initial screening questionnaire did
not include any questions regarding obsessions and com¬
pulsions or symptoms of inattention, impulsivity, or hy¬
peractivity. It was important to obtain an estimate of the
prevalence of OCD and ADHD in this sample to better
evaluate the rates of these two conditions among the in¬
dividuals with GTS. While our sample is quite small, it
can be used to determine the point prevalence of OCD
and ADHD in a random sample of 16- to 17-year-old in¬
dividuals in which all individuals were personally inter¬
viewed. Of the 562 inductees interviewed, 19 were di¬
agnosed as having OCD (3.4%), four (21.0%) of whom
had had tics at some point in their lives. A total of 22
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4. *OCD indicates obsessive-compulsive disorder; ADD, attention-deficit disorder; ADHD, attention-deficit hyperactivity disorder; minus sign, not present; and
plus sign, present.
individuals were determined to have a lifetime diagnosis
of ADHD (3.9%). Only one (4.5%) of these 22 had had
chronic tics.
COMMENT
To our knowledge, ours is the first population-based study
that has systematically screened a large unselected sam¬
ple for the presence of GTS. The overall prevalence esti¬
mate (4.2 per 10 000) we obtained is consistent with prior
estimates.4·5 This is somewhat surprising, because all pre¬
vious studies relied in some part on cases seen by a phy¬
sician or some other health care professional. In addition,
the sex ratio obtained was somewhat lower than that re¬
ported in previous studies. As noted, the prevalence was
estimated at 4.9 per 10 000 for males and 3.1 per 10 000
for females, resulting in a male-to-female ratio of 1.6:1.
This is different from the previous findings in which males
were at least three to four times more likely than females
to have GTS.
It is not immediately clear why the prevalence and
the sex ratio are so low. In all previous studies, individ¬
uals with GTS were identified through either health care
professionals or referral from special agencies. If there is
some referral bias, such that males are more likely than
females to be taken for help or put into special education
classes, then the ratio observed in these earlier studies
would be too large.
On the other hand, it is possible that the prevalence
estimates in our study are too low. Given the desirability
of being in the army in Israel, it is possible that these
individuals denied the existence of tics. However, the na-
ture of the induction process and the scrutiny of the eval¬
uation make it unlikely that an individual would be able
to suppress tics for the entire time of the assessment. Thus,
it is doubtful that denial is an important factor. Further¬
more, the results of the sensitivity study suggest that our
screening process was excellent for identification of sub¬
jects with GTS. However, it is still possible that a sub¬
stantial number of subjects denied ever having tics when
in fact that was not true. Because it was not possible to
obtain information from other sources (ie, family mem¬
bers, teachers, or peers), it was impossible to determine
with independent data whether tics did occur at some
earlier time.
Our findings are consistent with the hypothesis that
OCD is part of the clinical presentation of GTS in that
approximately 40% of all individuals with GTS were also
diagnosed as having OCD. Given that this is a sample of
16- to 17-year-old adolescents, this is probably an un¬
derestimate of the true frequency of OCD among patients
with GTS. It would be expected that some of these indi¬
viduals will eventually develop OCD.
In contrast, our findings do not support the hy¬
pothesis that ADHD is part of the clinical presentation
of GTS.13 Only one (8.3%) of the 12 subjects with GTS
was also diagnosed as having ADHD. This rate is not
significantly different from the rate obtained in this
population (3.9%). However, while these findings sup¬
port the hypothesis that the high rate of ADHD seen in
clinical samples of patients with GTS may result from
ascertainment bias similar to that described by Berk-
son14 and Pauls et al,15 a caveat must be noted. It is
very difficult to assess ADHD reliably. This is particu-
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5. larly true if the assessment is done in a retrospective
fashion, as was the case in our study. Furthermore, ad¬
olescents are not likely to be highly reliable reporters
of symptoms associated with ADHD. Unfortunately, no
other data were available regarding ADHD symptoms.
As discussed above, it was not possible to interview
parents, nor was it possible to obtain school or medical
records regarding childhood behavioral difficulties.
Thus, these findings must be interpreted with caution.
A much better research design to determine the rela¬
tionship between GTS and ADHD would include a
prospective longitudinal study of children at risk for
both disorders. It will only be possible to fully under¬
stand the relationship between the two conditions with
careful direct evaluation of children at risk with the
use of a variety of strategies designed to fully assess the
complete symptom profile of both disorders.
Although we screened a large sample of individu¬
als, the identified cohort of subjects with GTS is still
too small. Larger samples are needed so that analyses
that examine onset, severity, and course of illness can
be conducted for a non-clinic-based sample. Previous
work has suggested that only a minority of individuals
with GTS actually seek help for their disorder.5 Thus,
it is important to identify cases from additional epide¬
miologie studies so that it will be possible to under¬
stand more completely the full range of expression and
natural course of GTS.
Accepted for publication June 26, 1992.
This work was supportedin part bygrantsfrom the Tourette
Syndrome Association (Dr Apter, principal investigator), the
National Institutes of Health, Bethesda, Md (grant NS-
16648, Dr Pauls, principal investigator), and the National
Institute of Mental Health, Rockville, Md (grant MH-00508,
a Research Scientist Development Award to Dr Pauls).
The authors express appreciation to ProfY. Danon,former
chief of the Israel Defense Force Medical Corps, the physi¬
cians at the induction center where the sample was collected,
and Anat Hoffmanfor her contribution to the success of this
work. Finally, the authors express appreciation to two anon-
ymous reviewers for comments that substantially improved
the manuscript.
Reprint requests to the Child Study Center, Yale Uni¬
versity School of Medicine, 230 S Frontage Rd, New Haven,
CT 05610 (Dr Pauls).
REFERENCES
1. Cohen DJ, Bruun R, Leckman JF, eds. Tourette Syndrome and Tic Disorders:
Clinical Understanding and Treatment. New York, NY: John Wiley & Sons Inc;
1988.
2. Shapiro AK, Shapiro ES, Young JG, Feinberg T. Gilles de la Tourette Syndrome.
2nd ed. New York, NY: Raven Press; 1988.
3. Lucas AR, Beard CM, Rajput AH, Kurland LT. Tourette syndrome in Rochester,
Minnesota, 1968-1979. In: Friedhoff AJ, Chase TN, eds. Gilles de la Tourette
Syndrome. New York, NY: Raven Press; 1982:267-269.
4. Burd L, Kerbeshian J, Wikenheiser M, Fisher W. Prevalence of Gilles de la
Tourette's syndrome in North Dakota adults. Am J Psychiatry. 1986;143:787x=req-
788.
5. Caine ED, McBride MC, Chiverton P, Bamford KA, Rediess S, Shiao J. Tourette's
syndrome in Monroe County school children. Neurology. 1988;38:472-475.
6. Comings DE, Himes JA, Comings BG. An epidemiologic study of Tourette's
syndrome in a single school district. J Clin Psychiatry. 1990;51:463-469.
7. Pauls DL, Hurst CR. Schedule for Tourette's Syndrome and Other Behavioral
Syndromes. New Haven, Conn: Yale University Child Study Center; 1987.
8. Pauls DL, Raymond CL, Leckman JF, Stevenson JM. A family study of Tourette's
syndrome. Am J Hum Genet. 1991;48:154-163.
9. Jagger J, Prusoff BA, Cohen DJ, Kidd KK, Carbonari CM, John K. The epide-
miology of Tourette's syndrome: a pilot study. Schizophrenia Bull. 1982;8:
267-277.
10. Harcherick DF, Leckman JF, Detlor J, Cohen DJ. A new instrument or clinical
studies of Tourette's syndrome. J Am Acad Child Psychiatry. 1984;23:153x=req-
160.
11. Goodman WK, Rasmussen SA, Price LA, Mazure C, Heninger GR, Charney DS.
Yale-Brown Obsessive Compulsive Scale (Y-BOCS). New Haven, Conn: Yale
University School of Medicine; 1986.
12. Puig-Antich J, Orvaschel H, Tabrizi MA, Chambers W. The Schedule for Af-
fective Disorders and Schizophrenia for School-age Childrenp=m-EpidemiologicVer-
sion (Kiddie-SADS-E). 3rd ed. New York, NY, and New Haven, Conn: New York
State Psychiatric Institute and Yale University School of Medicine; 1980.
13. Comings DE, Comings BG. A controlled study of Tourette syndrome, I: atten-
tion deficit disorder, learning disorders and school problems. Am J Hum Genet.
1987;41:701-741.
14. Berkson J. Limitations of the application of fourfold table analysis to hospital
data. Biometrics. 1946;2:47-51.
15. Pauls DL, Hurst CR, Kidd KK, Kruger SD, Leckman JF, Cohen DJ. Tourette
syndrome and attention deficit disorder: evidence against a genetic relation-
ship. Arch Gen Psychiatry. 1986;43:1177-1179.
, on July 18, 2011www.archgenpsychiatry.comDownloaded from