A growing body of basic animal research and studies of abused and neglected children provide a strong basis of support for the hypothesis that individuals with particular genotypes are at greater risk for depression, anxiety disorders, and problems with the abuse of alcohol and other substances.
These gene-by-environment interactions are so powerful that some might assume that these genotypes identify people who are predestined to negative life outcomes.
However, a new study in the May 1st issue of Biological Psychiatry, published by Elsevier, challenges this view. Investigators studied infant monkeys from four different rearing conditions to examine how social context and different forms of early adversity interact with genotype to influence behavior.
Animals reared in small social groups were more likely to be aggressive and anxious, particularly among those with a low activity MAOA genotype. However, no genotype effects were evident in monkeys reared in larger social cages.
There are some circumstances in a child's development – such as abusive parenting – that everyone would agree constitutes "adversity." This study suggests, however, that other, more subtle features of the broader social environment influence development, and that genes that affect our behavioral responses are sensitive to these influences. So even though an infant may be reared with its nurturing mother, the relative absence of other social partners, for both the mother and the infant, can result in the infant developing an anxious style of responding to challenges, particularly if it possesses a "risky" genotype.