ADHD and Executive Functions: Emerging Concepts

Transcription

1 ADHD and Executive Functions: Emerging Concepts Thomas E. Brown, PhD Associate Director, Yale Clinic for Attention and Related Disorders Department of Psychiatry Yale Medical School

2 Shifts in Conceptualizing ADHD Hyperkinetic Disorder of childhood Attention Deficit Disorder With or without hyperactivity Residual type recognized ADHD (only combined symptoms) AD/HD 3 types AD/HD (impaired executive function)

3 Prevalence 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: Inheritance not specific to subtype CDC 2008; Kessler, 2006; Gaub M, Carlson CL. J Am Acad Child Adolesc Psychiatry. 1997;36(8): Levy F, et al. J Am Acad Child Adolesc Psychiatry. 1997;36(6): Smalley SL, et al. J Am Acad Child Adolesc Psychiatry. 2000;39(9):

4 ADHD Genetics: Heritability Coefficient Hudziak, 2000 Nadder, 1998 Levy, 1997 Sherman, 1997 Silberg, 1996 Gjone, 1996 Thapar, 1995 Schmitz, 1995 Edelbrock, 1992 Gillis, 1992 Goodman, 1989 Willerman, 1973 Breast cancer Asthma Schizophrenia Average genetic contribution of ADHD based on twin studies Faraone. J Am Acad Child Adolesc Psychiatry. 2000;39: Hemminki. Mutat Res. 2001;25: Palmer. Eur Resp J. 2001;17: Height ADHD Mean

5 What is ADHD? (A 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)

6 Executive 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

7 Brown TE. In press. Focus and Executive Function Impairments 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

8 Brown s s Model of Executive Functions Impaired in ADHD Symptom 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!

9 Brown s s Model of Executive Functions Impaired in ADHD Executive Functions Organizing, prioritizing, and activating to work Focusing, sustaining focus, and shifting focus to tasks Regulating alertness, sustaining effort, and processing speed Managing frustration and modulating emotions Utilizing working memory and accessing recall Monitoring and selfregulating action 1. Activation 2. Focus 3. Effort 4. Emotion 5. Memory 6. Action Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

10 1. 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; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

11 2. Focus, Shift, and Sustain Attention Loses focus when trying to listen or plan Easily distracted internal/external Forgets what was read, needs to re-read Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

12 3. Regulating Alertness, Effort, and 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; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

13 4. Manage Frustration, Modulate Emotion (Not included in DSM-IV criteria) 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 Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

14 5. Utilize Working Memory, Access Recall Difficulty holding one or several things on line while attending to 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; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

15 6. Monitor and Self-Regulate Action (Not just hyperactive/impulsive behavior) Difficulty controlling actions, slowing self and/or speeding up as needed for tasks Doesn t size up ongoing situations carefully Hard to monitor and modify own actions to fit situation/aims Brown TE. Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults; Brown TE. Manual for Attention Deficit Disorder Scales for Children and Adolescents; 2001.

16 What Requires Executive Functions? Tasks that involve managing oneself To prioritize, start, sustain, shift, stop, and integrate cognitive functions Using memory without moment-bymoment guidance from others Brown TE. In press.

17 Executive Functions: Development 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 noticeable by 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.

18 Executive Functions and Scaffolding 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

19 How Can Executive Functions 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

20 When Are ADHD Impairments Noticeable? Some are obvious very early and are noticeable in preschool years Some are not noticeable until middle elementary or junior high Some are not apparent until child leaves home to go to college or later

21 Challenges 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

22 Development of Brain Structures that 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.

23 Continuing Brain Development in Late 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): Benes FM, et al. Arch Gen Psychiatry. 1994;51(6):

24 Cortex 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)

25 Emotion 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)

26 EFs 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)

27 How Can Executive Function 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

28 Conflicting Models re: 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)

29 How Are EF Related to ADHD? 2 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

30 Some assume that Executive Functions are defined by neuropsychological 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):

31 Problems in Laboratory Measures of 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 ADHD subtypes. In: Rabbitt P, ed. Methodology of Frontal and Executive Function; 1997.

32 Elements 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

33 Elements 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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