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, 5 (5), e10621

Genetic Epidemiology of Attention Deficit Hyperactivity Disorder (ADHD Index) in Adults


Genetic Epidemiology of Attention Deficit Hyperactivity Disorder (ADHD Index) in Adults

Dorret I Boomsma et al. PLoS One.


Context: In contrast to the large number of studies in children, there is little information on the contribution of genetic factors to Attention Deficit Hyperactivity Disorder (ADHD) in adults.

Objective: To estimate the heritability of ADHD in adults as assessed by the ADHD index scored from the CAARS (Conners' Adult ADHD Rating Scales).

Design: Phenotype data from over 12,000 adults (twins, siblings and parents) registered with the Netherlands Twin Register were analyzed using genetic structural equation modeling.

Main outcome measures: Heritability estimates for ADHD from the twin-family study.

Results: Heritability of ADHD in adults is estimated around 30% in men and women. There is some evidence for assortative mating. All familial transmission is explained by genetic inheritance, there is no support for the hypothesis that cultural transmission from parents to offspring is important.

Conclusion: Heritability for ADHD features in adults is present, but is substantially lower than it is in children.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
Figure 1. Phenotype distribution of the ADHD index in men and women.
ADHD index scores were transformed into T-scores separately by sex.
Figure 2
Figure 2. Path diagram of phenotypic assortment model with genetic and cultural transmission from parents to offspring.
Squares represent the phenotypes of a DZ twin pair (PT1 and PT2) with one extra sibling (PSib), and both parents (PF and PM). Latent factors are represented by circles and include A (additive genetic factor), D (dominance genetic factor), and E (non-shared environment). F represents vertical cultural transmission whereby the phenotype of the parents influences the environment of their offspring. Assortment of parents is modeled as a copath (i). Simultaneous genetic and cultural inheritance induces a correlation (s) between this environmental factor F and the genetic factor A. Path coefficients a, d and e represent the influence of latent factors on the phenotype. The variance due to vertical cultural transmission is represented by r and the variance of additive genetic factors by g.

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