Plasticity genes, the social environment, and their interplay in adolescents with and without ADHD. From behaviour to brain

Attention-Deficit/Hyperactivity Disorder - ADHD - is strongly heritable, but influences of the social environment also plays an important role in interaction with genetic factors. Some genes have been posited to influence an individual’s susceptibility towards environmental experiences, so-called plasticity genes. This can be beneficial in a positive environment, but a disadvantage in negative environments. Richards investigated the effects of the social environment, genes, and their interplay on phenotypical, cognitive, and neural correlates of ADHD: social behaviour, reward sensitivity, response inhibition, and brain volumes. The results indicate that when focusing on reward sensitivity or response inhibition, the data lend support to differential susceptibility toward positive social environments based on one’s genotype. Moreover, Richards shows that for specific brain structures, gene-environment interactions can depend on age as well. Besides these interactions, several main effects were also found of the social environment on each included outcome measure. Importantly, most findings were similar for participants with and without ADHD, which suggests the effects of the social environment, genes, and their interaction contribute in a more general way to differences in social behaviour, reward sensitivity, response inhibition, and brain volumes.