Objectives: The purpose of this study is two-fold. First, we tested the association between dopamine D2 and D4 receptors and a trajectory of depressive symptoms in adolescence and young adulthood. Second, we reestimated the association between the dopamine receptors and depression after taking into account the effects of socioeconomic disparity and child-parent ties and social support.
Methods: The study uses the DNA sample of approximately 2500 individuals in the National Longitudinal Study of Adolescent Health (Add Health). Each individual was measured three times in 1994, 1996, and 2002.
Results: This study has yielded robust associations of the DRD2 and DRD4 variants with depressive symptoms among male adolescents and young adults. The DRD2*304/178 genotype is associated with a level of depressive symptoms 0.04-0.07 points (3-5% of the mean) higher than the DRD2*178/178 genotype. Relative to the other more common DRD4 variants, the DRD4*379/379 genotype raises the level of depression by about 0.25 points (about 17% of the mean). These findings hold after adjusting for the effects of socioeconomic status (family structure, parental education, family income, mother's employment status, and whether attending public school) and child-parent ties/social support (conflict with parent(s), closeness to parent(s), parental availability, and social support). Although the gene-sex interaction is clearly present, the tests of gene-lifecourse interaction did not yield any significant results.
Conclusion: Our findings emphasize the importance of joint influences of genetic propensities and social environment on depressive symptoms.