ADHD Netwerk Meeting, 16th June The nature and nurture of ADHD a developmental perspec7ve Corina Greven, PhD

Transcription

1 ADHD Netwerk Meeting, 16th June 2016 The nature and nurture of ADHD a developmental perspec7ve Corina Greven, PhD

2 Overview 1. Introduc7on to the nature-nurture debate 2. The nature and nurture of ADHD 3. Developmental aspects 4. Nature-nurture misunderstandings

3 % who think nature (genes) is at least as important as nurture (environments) Walker & Plomin, 2005

4 Nature nurture controversy One of oldest debates Un$l 1960s: View in favour of nurture dominated (e.g. schizophrenogenic mother) Now: Not genes versus environments genes and environments! How do we know?

5 Quan7ta7ve gene7cs Es7mates heritability. As much study of genes as of environments. Quantitative Genetic Research Designs Family Design Adoption Design Twin Design IVF Design e.g., e.g., e.g., e.g., First degree relatives Larger family pedigrees Adoptive vs. non-adoptive relatives Mono- vs. dizygotic twins Twins apart and together Parents who differ in genetic relatedness

6 Twin studies Monozygo'c (MZ) Dizygo'c (DZ) Gene'c similarity = 100% Gene'c similarity = 50% Logic: If MZ more similar than DZ twins à trait must be gene7cally influenced (= heritable)

7 Twin studies Es7mate the contribu7on of gene7c and environmental factors to individual differences (variance) in a trait. We typically es7mate: A: A Addi7ve gene7cs (heritability) C: C Common (shared) environment MZ 100% DZ 50% MZ 100% DZ 100% E: Environment specific to each twin (non-shared) E MZ 0% DZ 0% Shared or non-shared? Divorce? Shared classroom environment/ shared teacher? Differen7al effects of: accidents, percep7ons of environment, physical illness

8 Overview 1. Introduc7on to the nature-nurture debate 2. The nature and nurture of ADHD 3. Developmental aspects 4. Nature-nurture misunderstandings

9 Twin studies on ADHD High heritability of ADHD [1]. Liale evidence for ae7ological gender differences [2]. 2 dimensions: INATT and HYP- IMP [3-4]..50 A C E 70% 0% 30% ADHD (traits) A C E A C E 70% 0% 30% INATT 70% 0% 30% HYP-IMP [1] Burt 2009 Psychol Bull. [2] Greven submitted Oxford Handbook ADHD. [3] Greven 2011 J Abnorm Psychol. [4] Nikolas 2010 J Abnorm Psychol.

10 Twin studies: other child behavioural problems Trait/disorder Heritability (A) Shared environment (C) Non-shared environment (E) ADHD 70% 0% 30% Opposi7onal defiant problems Conduct problems 59% 10% 31% 58% 15% 28% Depression 44% 14% 42% Anxiety 48% 12% 40% Meta-analysis: Burt 2009 Psychol Bull

11 Twin studies on ADHD: rater effects Modest rater agreement [1]. Heritability parent > teacher > child-report [2]. à same vs different rater? Most (~80%) of associa7on between raters explained by shared genes [2]. A A A 80% 60% 50% ADHD traits (parent) ADHD traits (teacher) ADHD traits (child) [1] Derks 2006 Behav Genet. [2] Merwood Greven 2012 Psychol Med.

12 What genes explain the heritability of ADHD? Individual genes cannot explain high heritability of ADHD Maher 2008 Nature

13 SNP heritability SNP = single nucleo7de polymorphism SNP HERITABILITY Gene'c similarity SNP similarity of unrelated individuals Behavioural similarity If individuals who are more similar gene,cally, are also more similar behaviourally à trait is heritable All SNPs in the genome together. No specific genes.

14 SNP heritability individuals with ADHD controls % 30% Twin heritability SNP heritability 0 ADHD Explain almost half of twin heritability using DNA. Psychiatric Genomics Consortium 2013 Nature Genetics

15 Overview 1. Introduc7on to the nature-nurture debate 2. The nature and nurture of ADHD 3. Developmental aspects 4. Nature-nurture misunderstandings

16 Heritability of ADHD over 7me Heritability decreases? [1-2] Or stable? [3] % heritability shared environment Childhood Adolescence Adulthood [1] Boomsma 2010 Plos One. [2] Larsson 2013 Psychol Med. [3] Larsson 2014 Psychol Med.

17 Gene7c contribu7ons to developmental course HYP-IMP Childhood Adolescence Adulthood Childhood Adolescence Adulthood Greven 2011 J Abnorm Psychol.

18 Gene7c contribu7ons to developmental course > ½ of influence not shared > 8300 twin pairs, popula7on-based. E A A 80% E 20% Genes explained 80% of individual differences in change of HYP-IMP. HYP-IMP (parent-rated) Different genes involved in risk for HYP- IMP in childhood, and developmental course into late adolescence. age age 16 (= baseline) à Helps explain why some children with ADHD remit, others persist. Pingault Viding Galera Greven 2015 JAMA Psychiatry

19 90% of adults lacked childhood diagnosis of ADHD. May reflect different genes than childhood ADHD.

20 Why late-onset ADHD? Disorder may be masked in childhood? (protec7ve factors) ADHD-like symptoms caused by another disorder? A dis7nct disorder? (lower heritability, more women)

21 Overview 1. Introduc7on to the nature-nurture debate 2. The nature and nurture of ADHD 3. Developmental aspects 4. Nature-nurture misunderstandings

22 Nature nurture misunderstandings: right or wrong? 1. If gene7cs is important for ADHD, there is nothing you can do about it. 2. Heritability of ADHD is 70%. This means the disorder has gene7c origins in 70% of individuals with ADHD. 3. Low es7mates of shared environmental influences on ADHD mean that paren7ng does not maaer.

23 Nature nurture misunderstandings (1) If gene'cs is important, there is nothing you can do about it. (Wrong!) Genes are risk factors, not des7ny Weight (diet), phenylkentonuria (diet), ADHD (medica7on, parent management) QG research is about what is Not about what could be Not about what should be

24 Nature nurture misunderstandings (2) Heritability of ADHD is 70% à the disorder has gene'c origins in 70% of individuals with ADHD. (Wrong!) Heritability... does not refer to a certain individual, but to individual differences in the popula7on... es7mates the propor'on of variance (=individual differences) in a popula7on aaributable to gene7c differences A C E

25 Nature nurture misunderstandings (3) Low es'mates of shared environmental influences mean that paren'ng does not ma_er. (Wrong!) There are evidence-based paren7ng interven7ons (e.g. parent management for ADHD) Gene7c research provides new ways of thinking about the paren7ng environment (many environments are experienced differen7ally)

26 Take home message ADHD is 70% heritable. We can explain nearly half of this heritability using DNA( SNP heritability ). Gene7c factors may be involved in why some individuals with ADHD persist whereas others remit. Heritability does not refer to an individual, but to individual differences in the general popula7on. Genes are risk factors. Even highly heritable disorders can be highly responsive to environmental interven7on.

27 Thank you for your a_en'on!