Background: Genetic influences on stress reactivity may provide insight into depression risk mechanisms. The C-allele of rs6318, a putatively functional polymorphism located within the HTR2C gene, has been reported to predict greater cortisol and negative affective reactivity to lab-induced stress. However, the potential moderating effect of sex has not been examined despite X-linkage of HTR2C. We hypothesized that sex moderates the effect of rs6318 on cortisol and affective reactivity to lab-induced stress, with males showing stronger effects.
Methods: Non-depressed young adults (N=112; 39 female) screened via clinical interview provided a DNA sample and completed either a negative evaluative Trier Social Stress Test, or a non-evaluative control protocol. Salivary cortisol and self-reported affect were assessed at four timepoints.
Results: Contrary to hypotheses, C-carriers showed blunted rather than exaggerated cortisol responses to lab-induced stress in multilevel models (b=0.467, p<0.001), which persisted when covarying subclinical depressive symptoms. This effect was not moderated by sex (b=0.174, p=0.421), and remained significant when examining females (b=0.362, p=0.013) and males (b=0.537, p<0.001) separately. C-carriers also exhibited marginally greater reactivity in negative self-focused affect in response to stress than non-carriers when covarying subclinical depressive symptoms (b=-0.360, p=0.067), and exhibited higher levels of subclinical depressive symptoms than non-carriers (F=6.463, p=0.012).
Conclusions: Results support a role for the rs6318 C-allele in dysregulated stress responding, and suggest that the C-allele may contribute to risk for depression.
Keywords: Cortisol; Gene-environment interaction; Lab-induced stress; Major depressive disorder; Serotonin; rs6318.
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