This document discusses sluggish cognitive tempo (SCT) as a potential separate disorder from attention deficit hyperactivity disorder (ADHD). SCT is characterized by symptoms like daydreaming, mental confusion, and feeling slow and fatigued. The document reviews evidence that SCT has distinct symptoms, demographic profiles, cognitive correlates, impairments, and treatment needs compared to ADHD. While SCT often co-occurs with ADHD, particularly the inattentive presentation, the evidence suggests it may be a separate disorder warranting further study.

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3. The Other Attention Disorder:The Other Attention Disorder:
Sluggish Cognitive TempoSluggish Cognitive Tempo
vs. ADHDvs. ADHD
Russell A. Barkley, Ph.D.Russell A. Barkley, Ph.D.
Clinical Professor of PsychiatryClinical Professor of Psychiatry
Virginita Treatment Center for Children and VirginiaVirginita Treatment Center for Children and Virginia
Commonwealth University Medical CenterCommonwealth University Medical Center
Richmond, VARichmond, VA
©©Copyright by Russell A. Barkley, Ph.D., 2018Copyright by Russell A. Barkley, Ph.D., 2018
Email:Email: drbarkleydrbarkley@russellbarkley.org@russellbarkley.org
Websites: russellbarkley.orgWebsites: russellbarkley.org
ADHDLectures.orgADHDLectures.org

4. ObjectivesObjectives
• Discuss the history of Sluggish Cognitive Tempo, or
SCT and its emergence in research as a second
disorder of attention
• Review the current evidence concerning the nature
of SCT, its demographic findings, comorbidities,
impairments, and etiologies
• Present current theories on the nature of SCT,
particularly that it may represent a form of
pathological mind wandering
• Share what is known about the management of the
disorder

5. HistoryHistory
• Alexander Crichton (1798) refers to a second disorder of
attention distinct from an ADHD-like condition identified in
1775 by Melchior Adam Weikard. This second condition
involves low power of attention and arousal and limited
engagement with the environment
• Scientific research appeared in 1984 with efforts by Lahey,
Neeper, & Carlson to understand differences between ADD
with and without hyperactivity. A set of new symptoms being
tested for ADHD inattention was found to form a separate
dimension from ADHD, which was called SCT.
• Little research occurred on this as a separate condition from
ADHD until the past decade. Now an increasing number of
studies are focusing on SCT separately rather than as a
subtype of ADHD.
• Where does it fit into the current DSM-5 view of ADHD?

6. What About the Inattentive Presentation (ADD)?What About the Inattentive Presentation (ADD)?
DSM-5 Inattention Presentation
Inattentive
Formerly Combined
Types
Sub-threshold
Combined Types
Sluggish
Cognitive Tempo
View as always
Combined Types
View as milder
Combined Types
View as qualitatively
different type
30-50%

7. Is SCT A SeparateIs SCT A Separate
Disorder from ADHD?Disorder from ADHD?

8. The Criteria for Distinct DisordersThe Criteria for Distinct Disorders
Distinctions?
•Coherent symptom complex
•Demographic correlates
•Cognitive correlates
•Impairments
– (must be a harmful dysfunction – Wakefield, 1997)
•Comorbidity
•Etiology
•Family History
•Biological correlates (endophenotypes?)
•Course
•Treatment Response

9. Best SCT SymptomsBest SCT Symptoms
Becker, Burns, Schmitt, Epstein, & Tamm (2017),Becker, Burns, Schmitt, Epstein, & Tamm (2017), AssessmentAssessment, Epub ahead of print, Epub ahead of print
• 1. Behavior is slow (e.g., sluggish) (Factor loading = 0.92) ✔
• 2. Lost in a fog (0.89) ✔
• 3. Stares blankly into space (0.96) ✔
• 4. Drowsy or sleepy (yawns) during the day (0.95) ✔
• 5. Daydreams (0.88) ✔
• 6. Loses train of thought (0.86) ✖
• 7. Low level of activity (e.g., underactive) (0.97) ✔
• 8. Gets lost in own thoughts (0.81) ✔
• 9. Easily tired or fatigued (1.02) ✔
• 10. Forgets what was going to say (0.94) ✖
• 11. Easily confused (0.91) ✔
• 12. Lacks motivation to complete tasks (e.g., apathetic) (0.27) ✖
• 13. Spaces or zones out (0.82) ✔
• 14. Gets mixed up (0.85) ✖
• 15. Thinking is slow (0.87) ✔
• 16. Difficulty expressing thoughts (e.g., gets “tongue-tied”) (0.78) ✖

10. Symptoms on Barkley SCT Rating Scale*Symptoms on Barkley SCT Rating Scale*
1. Daydreaming excessively
2. Trouble staying alert or awake in boring situations
3. Easily confused
4. Spacey or “in a fog”; Mind seems to be elsewhere
5. Stares a lot
6. Lethargic, more tired than others
7. Underactive or have less energy than others
8. Slow moving or sluggish
9. Doesn’t seem to understand or process information as quickly or
accurately as others
10. Apathetic or withdrawn; less engaged in activities
11. Gets lost in thought
12. Slow to complete tasks
13. Needs more time than others (doesn’t discriminate from ADHD) ✖
14. Lacks initiative to complete work or effort fades quickly (same) ✖
*Barkley, R. A. (2017). Barkley Sluggish Cognitive Tempo Rating Scale – Children and Adolescents
(BSCTS-CA). New York: Guilford Press.

11. SCT Symptom CoherenceSCT Symptom Coherence
• SCT symptoms form a single construct that can be usefully
subdivided into 2+ related dimensions (factors)
– daydreamy-confused and
– sluggish/sleepy/lethargic
– The former are the more diagnostic from ADHD2
• SCT symptoms correlate moderately with ADHD IN
symptoms but weakly or even negatively with ADHD HI
symptoms
• Two dimensions correlate more with each other (.75) than
with ADHD Inattention (.40 -.50)
• Child self-reported SCT symptoms are reliable and show
moderate relations to parent and teacher ratings, unlike in
ADHD, and predict impairment in school and social
functioning beyond that of teacher and parent ratings.

12. Symptom Distinctions fromSymptom Distinctions from
Other DisordersOther Disorders
• SCT symptoms form a separate factor from
ADHD symptoms and other types of
psychopathology regardless of source (parent,
teacher, child, direct observations)
• Symptoms are especially distinctive from
disorders known to be comorbid with SCT, such
as depression, anxiety, and daytime sleepiness

13. Behavior
is
Slow
Drowsy
or
Sleepy
Underactive
Easily
Tired
Lost
in
Fog
Stares
Blankly
Daydreams
Lost
in
Thoughts
Spaces/Zones
Out
Loses Train
of
Thought
Forgets
What Say
Easily
Confused
Mixed Up
Thinking
Slow
Difficulty
Expressing
Thoughts
Sad
or
Depressed
Feels
Worthless
Seems
Lonely
Anhedonia
Feels
Hopeless
Low
Energy
Depression
SCT - Daydreaming/Spacy
SCT - Mental Confusion
SCT - Slow/Fatigue
Depression
SCT - Daydreaming/Spacy
SCT - Mental Confusion
SCT - Slow/Fatigue
SCT and Depression Symptoms
From Preszler, J., Burns, G. L.,
Servera, M., Saez, B., & Becker, S. P.
(May, 2018). A network analysis of
sluggish cognitive tempo and
depression symptoms in Spanish
children. Paper presented at the 30th
annual meeting of the Association for
Psychological Science, San Francisco,
CA. N = 2000 mothers. Use 15 SCT
and 6 depression symptoms

14. Demographic DifferencesDemographic Differences
• Prevalence is:
– 4-5% of children and adults in the U.S. (ages 5-89)
• ADHD is 7-10% of children and 3-5% of adults
– 21% of children seen in outpatient clinics have high SCT (Spain)
• Sex differences:
– Slightly greater occurrence of symptoms in males but no differences in
prevalence when SCT is cast as a disorder; ADHD is 3:1 (males > females)
in children, 1.6:1 or less in adults
• Age:
– Onset of SCT may be somewhat older than ADHD; not definitive
– Children meeting SCT criteria tend to be older than those with ADHD
– Slight increase in SCT symptoms with age but minor; decrease in ADHD
symptoms with age, especially the HI dimension
• SCT is associated more than ADHD with lower parental
education, lower household income, greater parental
unemployment or disability status, and more parent divorce

15. Cognitive DistinctionsCognitive Distinctions
• No inhibition problems or impulsiveness on ratings or on cognitive testing
in most studies
– If anything, they can be overly inhibited (a negative correlation with impulsiveness)
• Small or no significant relationship to IQ (-.15-.20)
– in ADHD, the relationship is modestly negative (r = -.30)
• Slow processing speed in young cases (<7) that may attenuate with age
– Is this a cognitive processing or motor response slowness or both?? Unknown
– More error prone (?)
– Slower mean reaction times (RT), more omission errors. In ADHD, greater RT
variability is commonplace
– Unlike ADHD-C type, sluggish style is cross-situational
• Poor focused or selective attention (slower to orient, less attention to
important task details)
• Little evidence for EF deficits on tests (inconsistent impact on working
memory); any such evidence shows far weaker relationships than is seen
in ADHD
• SCT has a small and inconsistent relationship to ratings of EF in daily life
such as in self-organization, planning, problem-solving (after controlling
for overlap with ADHD Inattention symptoms) (5% shared variance)

16. EF Ratings for SCT vs ADHDEF Ratings for SCT vs ADHD
(Barkley, 2013,(Barkley, 2013, Journal of Clinical Child & Adolescent PsychologyJournal of Clinical Child & Adolescent Psychology))
From Barkley, R. A. (2013). Journal of Clinical Child and Adolescent Psychology, 42, 161-173.

17. Percent of Variance in EF DimensionsPercent of Variance in EF Dimensions
Contributed by ADHD vs SCT SymptomsContributed by ADHD vs SCT Symptoms
From Barkley, R. A. (2013). Journal of Clinical Child and Adolescent Psychology,
42, 161-173.

18. Survey of US Adults (18-89)Survey of US Adults (18-89)
Contribution of ADHD vs SCT SymptomsContribution of ADHD vs SCT Symptoms
to Executive Functioning (% of variance explained)to Executive Functioning (% of variance explained)
From Barkley, R. A. (2012). Distinguishing sluggish cognitive tempo from attention deficit /hyperactivity disorder in adults. Journal of
Abnormal Psychology. 121(4), 978-990.

19. Contribution of SCT vs ADHD to EFContribution of SCT vs ADHD to EF
• ADHD Inattention accounts for 49-77% of variance
in all EF dimensions
• ADHD HI symptoms account for <1 to 6% of
variance, mainly in Self-Restraint and Emotional
Self-Regulation
• SCT accounts for less than 1% in each except Self-
organization, where it is 5%
• ADHD is vastly more associated with EF deficits in
daily life than is SCT
• SCT is NOT a pervasive disorder of Executive
Functioning; ADHD clearly is so.
• Findings largely replicated using BRIEF

20. Overlap of SCT with ADHDOverlap of SCT with ADHD
• In Children:
– 59% of SCT cases had any type of ADHD
– 39% of ADHD cases had SCT
• In Adults:
– 46% of SCT cases had ADHD of any type
– 54% of cases of ADHD have SCT, especially
if diagnosed with the Predominantly
Inattentive Type

21. School and Academic CorrelatesSchool and Academic Correlates
• Equally impaired as ADHD in school performance
• ADHD is more of a productivity disorder regarding school work while SCT
appears probably as an accuracy disorder
• The “Slow” dimension of SCT is most related to deficient achievement
skills
• Greater frequency of math disorders in SCT (related to low math
achievement ?)
– Math ability shares genetics with ADHD inattention also
• Contribution to school impairment is unique from ADHD3,6
• SCT symptoms contribute over time to increased student-teacher conflict,
especially in girls, that is unique from that associated with other disorders
• SCT contributes uniquely to motivational problems completing homework
independent of that made by ADHD and other disorders

22. Family and Social DistinctionsFamily and Social Distinctions
• Lower levels of general parenting stress (?)
– Why? Stress is linked to ODD and SCT is not linked to ODD
• Greatest parental concerns relate to homework and
school performance (not school behavior problems)
• Socially withdrawn, isolation, low initiative or even
anxious
– Less impaired socially than ADHD children
– SCT is related to lower social engagement in parent ratings (starting
conversations, joining activities) and more asociality/withdrawal, peer ignoring,
and more exclusion in teacher ratings
– ADHD-HI and ODD symptoms related to peer exclusion, being disliked, poor
self-control in social settings
• Contribution to social impairment is unique from
ADHD

23. Comorbidity and Personality TraitsComorbidity and Personality Traits
• Comorbidity: Rarely show aggression or ODD/CD
– May even have a negative correlation of SCT with ODD/CD symptoms
• Greater risk for internalizing symptoms
– More strongly linked to depression than anxiety, even after controlling for ADHD IN. And
increases risk for both disorders in children and adults even in those with ADHD. Also
may account for overlap of ADHD with anxiety and possibly depression
• Not more likely to have bipolar disorder than control children, unlike ADHD
• Equally as likely as ADHD to be associated with motor, spelling, & writing,
• As likely as ADHD to occur in autistic spectrum disorders and general
developmental delay, possibly even more so than ADHD in ASD.
– 64% of ASD kids have medium (33%) to high (31%) SCT symptoms
– Severity of SCT is linked to greater severity of ASD symptoms
– SCT was linked to greater social impairments and more internalizing symptoms
• 53% of SCT kids free of comorbidity vs. 39% of ADHD Only and 25% of
SCT+ADHD
• Linked to different personality traits than ADHD:
– ADHD linked to reward sensitivity and risk-taking
– SCT linked to punishment sensitivity and shyness/fear

24. Impairment in SCT vs ADHD ChildrenImpairment in SCT vs ADHD Children
* = SCT Worse than ADHD ! = ADHD Worse than SCT
*! ! ! ! ! ! ! ! !
From Barkley, R. A. (2013). Journal of Clinical Child and Adolescent Psychology, 42, 161-173.

25. Contributions of SCT vs ADHD to ImpairmentsContributions of SCT vs ADHD to Impairments
• ADHD results in impairment in twice as many domains as does SCT,
whether in kids or adults (5-7 vs. 2-3)
• ADHD Inattention (IN) contributes 49% of variance to Home-School
Impairment in children (SCT = 1%)
• ADHD HI symptoms contribute 35% of variance to Community-Leisure
impairment in children (SCT = 6%)
• ADHD IN contributes 34% of variance to pervasiveness of impairment (#
domains) whereas (ADHD-HI = 5% and SCT is <2%
• ADHD is a far more impairing disorder than SCT producing more
pervasive impairment as well; but SCT is still impairing
• ADHD children had a greater percentage having teacher complaints of
school problems (72-85%), had lower grade point averages, and were
more likely to be retained (8-25%)
• When comorbid, SCT contributes additional risks for impairment beyond
that accounted for by ADHD – disorders appear to be additive

26. Impairments in SCT vs. ADHD AdultsImpairments in SCT vs. ADHD Adults
*SCT is worse than ADHD; ! ADHD is worse than SCT
Even so – regression analyses indicate that ADHD contributes 40% of the variance to overall mean impairment
and 32% to number of impaired domains (pervasiveness) while for SCT it is 3% and 2%, respectively, just as in
the survey of US children
From Barkley, R. A. (2012). Distinguishing sluggish cognitive tempo from attention deficit /hyperactivity disorder in adults. Journal of
Abnormal Psychology. 121(4), 978-990.
*
*
!

27. Further Adult DifferencesFurther Adult Differences
Overlapping but distinct conditions
SCT
Hypersomnia
ADHD

28. Possible EtiologiesPossible Etiologies
• Research is very sparse and limited
• EEG - One study shows that only ADHD is linked to higher
theta/beta ratio in the frontal region on EEG while SCT
symptoms are not. Reduced ERP at 100ms; ADHD is 300ms?
• Heart rate variability - A recent study in China shows greater
resting heart rate variability (HRV) and larger increases in
HRV in response to warning stimuli to be linked to SCT
symptom severity
• Neuro-Imaging - two studies have found higher symptoms of
SCT to be linked to problems with the activation of the Default
Mode Network (DMN) and its functional connectivity. ADHD is
associated more with dysfunction in executive networks that
create secondary problems in management of the DMN.

29. Default Mode NetworkDefault Mode Network

30. More on EtiologiesMore on Etiologies
• FAE/FAS - SCT symptoms occur more often in
prenatally alcohol exposed children and childhood
leukemia
• Genetics - Recent genetic (heritability) research
shows that SCT is:
– moderately heritable but somewhat less than is ADHD (.60 vs. .76)
– a greater contribution of unique environmental events to symptom variation.
– Some shared genetic liability between the two types of inattention but also
some unique genetic contribution to SCT as well.
• Psychosocial Adversity - SCT is also linked to
greater family and child psychosocial adversity;
thus social stressors may be more linked to SCT
than ADHD

31. What is the Nature of SCT?What is the Nature of SCT?
• It appears to be a distinctly different form of inattentiveness
from that seen in ADHD
• Possibly a dysfunction of arousal or a hypersomnia?
– Doubtful given Langberg et al. (2013) study with college students showing it
overlaps with but is distinct from daytime sleepiness
• Possibly a disorder of the focus/execute or stabilize attention
components?
• Possibly excessive mental preoccupation or rumination
related to social stressors, anxiety, OCD?
– No – research shows excessive dissociative absorption in imaginative
or external stimuli (movies, books, etc.) is related to OCD, not ADHD
• Maybe a case of pathological mind wandering or maladaptive
daydreaming?
• Adams, Z. & Milich. R. (2012). The ADHD Report

32. SCT as a Disorder of Mind Wandering?SCT as a Disorder of Mind Wandering?
• Mind wandering or maladaptive daydreaming is the shifting of
attention away from external events and toward internal mental
events. It can be deliberate or spontaneous. When spontaneous, it is
highly related to activity in the Default Mode Network of the brain.
• When intentional it can be constructive. Under some circumstances it
can coexist with other goal directed behavior, like a divided attention
task. This can occur when more routine goals are being largely
automatically pursued – it is an efficient use of excess EF capacity
(especially working memory) in which one intentionally focuses on
various thoughts, such as other goals, problems, or concerns, while
engaged in a separate goal-directed action
• When it is engaged in spontaneously and excessively, it can diminish
the EF capacities needed for the primary goal-directed action and
even interfere with the primary task or goal, slowing progress toward
the goal, increasing errors, or even preventing the goal from being
attained or the task being completed in time.

33. Different Types of ThoughtDifferent Types of Thought
Christoff, K. et al. (2016). Mind-wandering as spontaneous thought: a dynamic framework.Christoff, K. et al. (2016). Mind-wandering as spontaneous thought: a dynamic framework.
Nature Reviews: NeuroscienceNature Reviews: Neuroscience. Epub ahead of print.. Epub ahead of print.
Strong
Weak
Strong
Deliberate Constraints – contents of thought are under executive cognitive control
Automatic Constraints are a result of a family of mechanisms operating outside of cognitive
control, such as sensory or affective salience. Each of the three forms of thought can be
externally or internally oriented.
Rumination and Obsessive Thought
Spontaneous Thought
Dreaming Mind Wandering
Creative
Thinking
Goal-directed
Thought

34. Do Medications Treat SCT?Do Medications Treat SCT?
• Most drug research was with methylphenidate and used ADD
without H child cases (or Inattentive Only) – not selected
specifically for SCT
– They found ADHD IN to be Less Likely to Have a Clinically Impressive Response to
Stimulants (based on a few studies of ADHD IN type)
– Barkley (1991) found 65% improved modestly in symptom ratings but only 20% showed a
good clinical response warranting continued medication; low dose was best
• But a recent study at Cincinnati Children’s Hospital showed that SCT
Sluggish symptoms predicted a lower or non-response to MPH while SCT
Daydreamy symptoms had no relation to MPH response.
• Just one study of SCT symptoms in children treated with atomoxetine
– Study by Wietecha et al. (2013) shows significant improvement in SCT in
children with ADHD+dyslexia and those with ADHD only on parent and teacher
SCT ratings.
– New research also shows that ATX binds with serotonin transporter, not just NE
transporter
• If SCT is ruminative or related to OCD would other relevant
medications be useful? Unknown
• If SCT is related to hypersomnia or arousal problems, again
would other relevant medications be useful? Unknown

35. Psychosocial Treatment ConsiderationsPsychosocial Treatment Considerations
• Good (better?) response to joint home-school treatments
– MTA study: anxious cases did the best in psychosocial treatment
– Several studies by Pfiffner show that a combined home-school behavioral
program focusing on social and organizational skills and that is targeted at
ADHD-I specific problems can be effective.
– Best response in Pfiffner studies was found in children with higher IQs (105+),
whose parents were low in anxiety/depression or ADHD symptoms, and in
children with lower hyperactivity impulsivity symptoms.
• Better response to social skills training? Used ADHD-I type
children compared to ADHD-C cases
– Improved only assertion in both groups but more in I-types
– Up to 25% of ADHD cases become more aggressive in social skills
groups due to peer deviancy training*
• More responsive to cognitive therapy?
– It doesn’t work for ADHD kids but if this is not ADHD then try it again?
– It does work for anxiety disorders and depression
• Obviously, comorbid disorders (depression, anxiety, LD,
ADHD) will require separate management

36. SCT is Not an Appropriate LabelSCT is Not an Appropriate Label
• Implies we know the core cognitive deficit in the
disorder – we don’t
– No studies on timing or processing in SCT
• Could be construed as derogatory or offensive
– slow witted? lazy?
• ADD has been suggested but just creates confusion
– ADD was term for ADHD in 1980s
• Pathological mind wandering? Too soon to say
• Why not Concentration Deficit Disorder?
– Implies attention problem but not specific dysfunction
– General enough not to be offensive
Saxbe, C. & Barkley, R. A. (2013). Journal of Clinical Psychiatry, in press.
Barkley, R. A. (2013). Journal of Abnormal Child Psychology. Special Issue on SCT

37. SummarySummary
• ADHD is a chronic disorder of inhibition, inattention, and poor self-
regulation (EF)
• SCT (ADD) seems to be a different disorder from ADHD and not a
subtype of it
• Both disorders can be comorbid and are impairing though they may
differ in which major life activities they create the greatest impairment
and in how they impair them
• ADHD contributes far more to EF deficits than does SCT but
contribution of SCT increases in adulthood
• In children and adults, ADHD is a more impairing disorder and more
pervasively impairing but SCT can be worse than ADHD in selective
situations
• Regardless of disorder status, SCT is a valuable trans-diagnostic
construct making a unique contribution to many important variables
(comorbidity, impairment, neuropsychology, etc.)
• So, is SCT a distinct disorder from ADHD?

38. Does SCT meet criteria for a distinct disorder?Does SCT meet criteria for a distinct disorder?
Coherent and distinct symptom complex –Yes
Distinct demographic correlates - Yes
Distinct cognitive correlates – Probably
Distinct impairments – Probably, SCT is also milder
Distinct pattern of comorbidity - Yes
Distinct biological correlates - Unknown
Distinct course – Unknown
Distinct etiologies – Maybe, not enough evidence
Distinct family history - Unknown
Distinct pattern of treatment responses – Unknown