A decade of research has demonstrated the explanatory potential of interplay between genetic variants and environmental factors in the development of common mental disorders. Initial findings have undergone tests of replicability and specificity. Some gene-environment interactions have been confirmed, some have not replicated and yet other turned out to be more specific than initially thought. Specific and complementary roles of genetic factors have been delineated: a common functional length polymorphism in the serotonin transporter gene (5-HTTLPR) moderated the effect of childhood maltreatment on chronic depression in adulthood, but did not substantially influence the effects of adult stressful life events on the onset of new depressive episodes; in contrast, a common functional polymorphism in the brain-derived neurotrophic factor gene (BDNF) moderated the effect of stressful life events in adulthood in triggering new depressive episodes, but did not influence the effects of childhood maltreatment. Molecular mechanisms underlying gene-environment interactions are being uncovered, including DNA methylation and other epigenetic modifications. New gene-environment interactions continue to be reported, still largely from hypothesis-driven research. Statistical and biological prioritization strategies are proposed to facilitate a systematic discovery of novel gene-environment interactions in genome-wide analyses.