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Class # 3: Neurobiology of ADHD

Class # 3: Neurobiology of ADHD

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Class # 3: Neurobiology of ADHD

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  1. The Psychology & Education of Students with ADHD [HDP3238H] Class # 3: Neurobiology of ADHD Class#1: Historical & current concepts of ADHD; diagnostic criterion for ADHD Class #2: Developmental / Lifespan and sex differences in ADHD

  2. Plan for today • Review Ticket-out-of-the-Door (Class #2) • Review of statistical concept (ES) • Update on DSM-V (age-of-onset) • Review of today’s readings • (small group activity) • Didactic: neurobiology of ADHD • Brain differences • Cognitive differences

  3. Summary #2:Ticket-Out-The-Door (n=14) • New & Significant for you • “g” factor of ADHD (5) • Negative adolescent & adult outcomes of ADHD (4) • Issues pertaining to subtypes (3) • Unclear/request more information • Statistical terminology & concepts (6)

  4. Statistical concepts • Effect sizes • Odds Ratio • Cohen’s d • Hedges ‘g’ effect size Koffler et al (2009) ADHD and Working Memory…..

  5. Statistical concepts: Power • The probability that a study will detect meaningful (significant) differences if they exist • Ideally a study should have power level ≥ 0.80, meaning an 80% chance of finding an effect • Power depends on • Sample size (number of participants; rule of thumb is at least 30 per group) • Effect size • Precision of measures

  6. DSM-V Update Age-of-onset

  7. What is the validity of Criterion B ?“Age-of-Onset of ADHD symptoms” • Criterion B: Some hyperactive/impulsive or inattentive symptoms that caused impairment were present before age 7 years. (Introduced in DSM-III) • Data base: systematic literature search • 31 studies reporting original data on age of onset (Kieling, Kieling, Rohde, Frick, Moffitt, Nigg, Tannock, Castellanos (2010). Am J Psychiatry 167: 1 )

  8. Evidence against Criterion B • Analysis of DSM-IV field trials revealed later onset for inattentive group • Adult population study revealed that only 50% individuals with ADHD retrospectively recalled an onset before 7 years • Prospective studies reveal poor stability of recall of age of onset • Series of studies reveal that later-onset ADHD does not differ from before-age-7-onset in comorbidity, neuropsychological profile, impairment, treatment response

  9. What is your vote for age-of-onset? • Keep as is (onset before age 7 years) • Modify to “onset before age 12” • Modify as “onset before age 18” (broadly interpreted as the developmental period) • No specification of age

  10. Provisional recommendations by DSM-V Work Group on ADHD • In the absence of a scientific basis for the existing age of onset criterion, modify the current age-of-onset (age 7) to a later time (age 12) • What are the implications of changing Criterion B? • Polanczyk (2010) concluded that raising the age of onset to age 12 would not increase prevalence rates of the disorder (J Am Acad Child Adolesc Psychiatry 49: 210)

  11. Small Group Activity: today’s readings • Discuss & summarize major findings of the study • Discuss & identify the major implications for education • Role play • SERT, classroom teachers • Teachers complain about difficulty handling a student’s ‘disruptive behavior’ (inattention, hyp/imp) • SERT explains study findings & suggests ways to help the teacher

  12. The other ‘face’ of ADHD • Behavioral & mental health perspective • Neurobiological perspective

  13. Causes of ADHD Other Perinatal factors Smoking Lead Fetal Alcohol exposure Heritable (Genetics) Prematurity Low birth weight

  14. 0 0.2 0.4 0.6 0.8 1 ADHD Mean Schizophrenia Asthma Height Breast cancer Hudziak, 2000 Twin Studies Show ADHD Is a Genetic Disorder Nadder, 1998 Levy, 1997 Sherman, 1997 Silberg, 1996 Gjone, 1996 Thapar, 1995 Schmitz, 1995 Edelbrock, 1992 Gillis, 1992 Goodman, 1989 Willerman, 1973 Average genetic contribution of ADHD based on twin studies 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.

  15. Between 40-60% of parents with ADHDwill have a child with the disorder • 25% of children with ADHD will have a parent or sibling with ADHD • There is an added challenge of raising a child with ADHD when the parent has the disorder ADHD: A Family Affair Murray & Johnston, J Abnorm Psychol, 2006; Sonuga-Barke et al. Am Acad Child Adolesc Psych, 2002

  16. Temporal and Spatial Resolution of Brain Imaging Techniques image from: http://www.4dneuroimaging.com/BasicPrinciples.html

  17. Brain differences in ADHD occur in regions that are important for attention, self-regulation, and learning Frontal cortex: Controls the ways we think, act, and pay attention, including planning, organizing, and monitoring behaviour. Parietal cortex: Interpret visual-spatial information about our environment and sensations and messages from other parts of the brain. They help us understand shape, size, direction, the representation of numbers and quantity. Basal Ganglia A collection of nuclei Involved in moment-to-moment motor control (action selection) and learning. Cerebellum Controls our posture, balance, coordination, and movement. For example, it controls exact timing as required for actions such as walking and playing the piano. R. Tannock: HSC Toronto/ Public Education Program: Kelowna, British Columbia (Nov 2005)

  18. Delayed brain growth in ADHD (3 yrs.) Educational Implications Keep in mind a possible 2-3 year discordance between chronological age & self-regulatory ability in children & adolescents with ADHD Greater than 2 years’ delay 0 to 2 years delay Ns: ADHD=223; Controls = 223

  19. Altered brain activation & functional connectivity in adults with ADHD during the delay period of a WM taskWolf et al (2009) Human Brain Mapping What do you understand by the term “working memory” ? First, a paired-activity on WM….

  20. Altered brain activation & functional connectivity in adults with ADHD during the delay period of a WM taskWolf et al (2009) Human Brain Mapping What do you understand by the term “working memory” ? First, a paired-activity on WM

  21. Altered brain activation & functional connectivity in adults with ADHD during the delay period of a WM task

  22. ADHD: slow & effortful processing Geneticfactors Environmental Factors (eg maternal smoking) Insufficient neurotransmitter (during effortful processing) Insufficient neuronal function Inefficient & effortful brain function