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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