ADHD and ADHD and Executive Functions: Executive Functions: Emerging ConceptsEmerging Concepts
Thomas E. Brown, PhDAssociate Director,
Yale Clinic for Attention and Related DisordersDepartment of Psychiatry
Yale Medical School
Shifts in Conceptualizing ADHDShifts in Conceptualizing ADHD 1968 Hyperkinetic Disorder of childhood
1980 Attention Deficit Disorder
1987 ADHD (only combined symptoms)
1994 AD/HD–3 types
2000 AD/HD (impaired executive function)
• With or without hyperactivity
• Residual type recognized
Prevalence and Genetics of ADHDPrevalence and Genetics of ADHD
9% of children; 4.4% of adults Male-female: 6:1, 3:1, 1:1 All levels of IQ All levels of socioeconomic status Family genetic transmission: 7.5 – 8.0 Inheritance not specific to subtype
CDC 2008; Kessler, 2006; Gaub M, Carlson CL. J Am Acad Child Adolesc Psychiatry. 1997;36(8):1036-1045. Levy F, et al. J Am Acad Child Adolesc Psychiatry. 1997;36(6):737-744. Smalley SL, et al. J Am Acad Child Adolesc Psychiatry. 2000;39(9):1135-1143.
Faraone. J Am Acad Child Adolesc Psychiatry. 2000;39:1455-1457. Hemminki. Mutat Res. 2001;25:11-21.Palmer. Eur Resp J. 2001;17:696-702.
Willerman, 1973
Goodman, 1989
Gillis, 1992
Edelbrock, 1992
Schmitz, 1995
Thapar, 1995
Gjone, 1996
Silberg, 1996
Sherman, 1997
Levy, 1997
Nadder, 1998
Hudziak, 2000
Average genetic contribution of ADHD based on twin studies0 0.2 0.4 0.6 0.8 1
HeightBreast cancer Asthma Schizophrenia
ADHD Genetics: Heritability CoefficientADHD Genetics: Heritability Coefficient
ADHD Mean
What is ADHD?What is ADHD?((A Controversial Viewpoint)A Controversial Viewpoint)
ADHD (all subtypes) = Developmental Impairment of Executive Functions
Developmental Impairment =(Not emerging and unfolding as expected for age)
Attention Deficit Disorder: The Unfocused Mind in Children and Adults
(T.E. Brown, Yale University Press, Sept, 2005)
Executive FunctionsExecutive Functions
Wide range of central control processes of the brain
Connect, prioritize, and integrate cognitive functions–moment by moment
Like conductor of a symphony orchestra
““Focus” and Executive FunctionFocus” and Executive FunctionImpairments of ADHDImpairments of ADHD
In DSM-IV “inattention” symptoms of ADHD•Do not mean
• Unable to focus as in holding the camera still to take a photo of an unmoving object
•Do mean• Unable to focus as in focusing
on the task of driving a car
Brown TE. In press.
Brown’s Model of Executive Functions Brown’s Model of Executive Functions Impaired in ADHDImpaired in ADHD
Symptom CharacteristicsSymptom Characteristics
Dimensional, not “all-or-nothing”• Everyone sometimes has some impairments in these functions; in ADHD, it is a chronic, severe impairment
Situational variability: “If I’m interested”• Most persons with ADHD have a few activities where ADHD impairments are absent
ADHD looks like a willpower problem, but it isn’t!
Brown’s Model of Executive Functions Brown’s Model of Executive Functions Impaired in ADHDImpaired in ADHD
Executive Functions
Organizing, prioritizing,
and activatingto work
1.Activation
Focusing, sustaining focus, and
shifting focus to tasks
2.Focus
Regulating alertness, sustaining effort, and processing
speed
3.Effort
Managing frustration
and modulating emotions
4.Emotion
Utilizing working
memory and accessing
recall
5.Memory
Monitoring and self-
regulating action
6.Action
Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
1. Organize, Prioritize, and Activate1. Organize, Prioritize, and Activate
Difficulty organizing tasks, materials
Difficulty estimating time, prioritizing tasks
Trouble getting started on work
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
2. Focus, Shift, and Sustain Attention2. Focus, Shift, and Sustain Attention
Loses focus when trying to listenor plan
Easily distracted–internal/external
Forgets what was read, needsto re-read
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
3. Regulating Alertness, Effort,3. Regulating Alertness, Effort,and Processing Speedand Processing Speed
Difficulty regulating sleep and alertness Quickly loses interest in task, especially
longer projects; doesn’t sustain effort Difficult to complete task on time,
especially in writing–“slow modem”
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
4. Manage Frustration,4. Manage Frustration,Modulate EmotionModulate Emotion
Emotions impact thoughts, actions too much
Frustration, irritations, hurts, desires, worries, etc., experienced “like computer virus”
“Can’t put it to the back of my mind”
(Not included in DSM-IV criteria)
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
5. Utilize Working Memory,5. Utilize Working Memory,Access RecallAccess Recall
Difficulty holding one or several things “on line” while attendingto other tasks
Difficulty “remembering to remember” Inadequate “search engine” for activating
stored memories, integrating these with current info to guide current thoughts and actions
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
6. Monitor and Self-Regulate Action6. Monitor and Self-Regulate Action
Difficulty controlling actions, slowing self and/or speeding up as neededfor tasks
Doesn’t size up ongoing situations carefully
Hard to monitor and modify own actions to fit situation/aims
(Not just hyperactive/impulsive behavior)
Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000. Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.
What Requires Executive Functions?What Requires Executive Functions?
Tasks that involve managing oneself
To prioritize, start, sustain, shift, stop, and integrate cognitive functions
Using memory without moment-by-moment guidance from others
Brown TE. In press.
Executive Functions:Executive Functions:Development and DemandsDevelopment and Demands
EF capacity develops through childhood, into adolescence, and beyond; it is not fully present in early childhood
Environmental demands for EF increase with age, from preschool through adulthood
EF impairments often are not noticeableby age 7!
Brown TE. Emerging understandings of attention deficit disorders and comorbidities. In: Brown TE, ed. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; 2000:3-55.
Executive Functions and Executive Functions and ScaffoldingScaffolding
In early childhood, others perform all executive functions for the child (parents, teachers, sibs and other caretakers)
Scaffolding is provided by showing, directing, helping, reminding, coaching, critiquing
(Examples: walking, getting dressed, crossing street, riding bike, driving car)
Scaffolding is gradually withdrawn, as child becomes able to (or is forced to) perform these functions for self
In adolescence & adulthood scaffolding may be provided by: friends, teachers, coaches, spouses, supervisors
How Can Executive FunctionsHow Can Executive FunctionsBecome Impaired?Become Impaired?
Developmentally, eg, ADHD Trauma, eg, traumatic brain injury Disease, eg, Alzheimer’s disease In trauma and disease, the patient
usually has had adequate EF, then loses it
In ADHD, EF has not developed adequately
When Are ADHDWhen Are ADHDImpairments Noticeable? Impairments Noticeable?
Some are obvious very early andare noticeable in preschool years
Some are not noticeable untilmiddle elementary or junior high
Some are not apparent until child leaves home to go to college or later
Challenges May Reveal WeaknessesChallenges May Reveal Weaknesses
Cardiac weaknesses may not be noticeable in EKG taken while lying quiet on a table, but may be very noticeable while playing basketball, shoveling snow
EF weaknesses may not be noticeable until one’s self-management is challenged by increased demands of adult life
Development of Brain Structures Development of Brain Structures that Support Executive Functionsthat Support Executive Functions
Structures and functions that support EF are not fully developed at birth
Neural networks underlying effortful control begin development at 2-4 years old, but don’t fully develop until one’s 20s
Development of EF capacities continues into early adulthood
Rothbart MK, Posner MI. Mechanism and variation in the development of attentional networks.In: Nelson CA, Luciana M, eds. Handbook of Developmental Cognitive Neuroscience; 2001.
Continuing Brain Development in Continuing Brain Development in Late Childhood and AdolescenceLate Childhood and Adolescence
Between 6-15 years, extreme growth (to 80%) occurs at the collosal isthmus that supports associative relay, while considerable synaptic pruning occurs
Brain myelination increases 100% during the teenage years
Dopamine (DA), norepinephrine (NE), and serotonin (5-HT) transmitter systems in the brain continue to develop into one’s 20s
Thompson PM, et al. Nature. 2000;404(6774):190-193.Benes FM, et al. Arch Gen Psychiatry. 1994;51(6):477-484.
Cortex Maturation in ADHD vs NCCortex Maturation in ADHD vs NC
MRI studies of 40K cortex sites in 223 youths with ADHD vs matched controls
Brain maturation was delayed ~3yrs in specific regions in ADHD youths vs NC
Frontal areas of cortex slower in ADHD Medial PFC developed lagged 5 yrs
(Shaw, et al, PNAS, Nov, 2007)
Emotion regulates EFsEmotion regulates EFs
“All information processing is emotional …emotion is the energy level that drives, organizes, amplifies & attenuates cognitive activity.” (K. Dodge, 1991)
Emotional value is automatically, uncsly assigned to stimuli (amygdala, medial PFC)
[how threatening, important, interesting is this?]
(Damasio, 1994, 1999; LeDpux, 1996, 2002,)
Brain imaging studies show reciprocal connections via medial PFC between emotion and cognition, anxiety/dysphoria & attention
(Mayberg, et al, 1999; Simpson, et al, 2001)
EFs regulate emotionEFs regulate emotion
Brain imaging of NC shows “gating” of emotion to reduce affective interference during more valued/complex cognitive tasks.
(Pochon, Levy, et al, 2002)
Many persons with ADHD self-report chronic impairment in their ability to modulate affective interference in daily life. This is consistent with their other EF impairments
(Brown, 1996, 2001)
How Can Executive FunctionHow Can Executive FunctionImpairments of ADHD Be Assessed?Impairments of ADHD Be Assessed?
When ADHD was seen as just a disruptive behavior disorder in childhood, diagnosis was based on observing overt behavior
EF impairments of ADHD are largely cognitive, covert, and not easily observed
Performance of complex, everyday tasks may be a more sensitive diagnostic indicator of EF impairments
Conflicting ModelsConflicting Modelsre: How to assess EF impairmentsre: How to assess EF impairments
1. Neuropsych tests of EF: WCST, Stroop, Rey-Ost., Tower of
Hanoi, etc. (Wilcutt, et al, 2005)
2. Clinical interviews re: past/present self-management of daily life (Barkley, 1997, Brown, 2005)
(Brown, 2006)
How Are EF Related to ADHD? How Are EF Related to ADHD? 2 Conflicting Models2 Conflicting Models
Partial overlap (~30%) EF impairments as characteristic of some individuals with ADHD, but not essential to the disorder (Willcutt, et al. 2005)
Full overlap (100%)
-Combined subtype only (Barkley) - All subtypes (Brown)
Brown TE. 2006.
Some assume that Some assume that Executive FunctionsExecutive Functionsare defined by neuropsychological are defined by neuropsychological
“tests of EF”“tests of EF” Single neuropsychological measures are
not effective in identifying ADHD in children or adults
Multiple tests improved diagnosis efficiency (high positive predictive power, modest negative predictive power)
Multiple tests show about 30% of those with ADHD are impaired on EF
Doyle AE, et al. J Consult Clin Psychol. 2000;68(3):477-488.
Problems in Laboratory Measures of Problems in Laboratory Measures of Executive Functions (“Streetlamp Problem”)Executive Functions (“Streetlamp Problem”) Most research tries to isolate, quantify,
and measure effects of a single variable presumed to tax a single functional process
This strategy is inappropriate for EF “because an essential property of all “executive” behavior is that, by its nature, it involves simultaneous management of a variety of different functional processes”1
1. Rabbitt P. Methodologies and models in the study of executive functions and DSM-IV ADHDsubtypes. In: Rabbitt P, ed. Methodology of Frontal and Executive Function; 1997.
Elements of a New Paradigm for ADHDElements of a New Paradigm for ADHD
1. ADD = developmental impairment of uncs self-management system of brain
2. Self-regulation of and by emotion is impaired in ADD
3. ADD sx may be noticeable in childhood, but often not apparent until challenges of adolescence/adulthood
Elements of a New Paradigm for ADHDElements of a New Paradigm for ADHD
4. ADD appears to be insufficient willpower, but is actually a problem of chemical dynamics in brain
5. Causes of ADD are primarily genetic, but environmental stressors & supports modify sx expression
6. ADD is a foundational disorder that increases lifetime risk of other disorders.
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