Dopamine and serotonin systems modify environmental effects on human behavior: a review.

The relative influences of genetic and environmental factors in the development of human behavior have been a long-term topic for an intense debate. Recent behavioral genetic studies suggest focusing on the joint effect of genes and environment, and especially on the life-course developmental interplay between nature and nurture. Vulnerability to environmental adversities and sensitivity to its benefits may be conditional on genetic background, and regarding psychological outcomes, these kinds of gene x environment interactions may be of higher importance than direct gene-trait associations. In our recent series of studies, we have shown that different variants of serotonergic and dopaminergic genes may moderate the influence of environmental conditions on a range of psychological outcomes, i.e. temperament, depression, hostility, and educational attainment. These studies suggest that depending on their genotype, people may be differentially sensitive to the environmental conditions they encounter. In the light of these results it seems highly plausible that the effects of genes may become evident only when studied in the context of environmental factors.