Social constraints, genetic vulnerability, and mental health following collective stress.

A repeat-length polymorphism of the serotonin promoter gene (5-HTTLPR) has been associated with depression and posttraumatic stress disorder (PTSD) in trauma-exposed individuals reporting unsupportive social environments. We examine the contributions of the triallelic 5-HTTLPR genotype and social constraints to posttraumatic stress (PTS) symptoms in a national sample following the September 11, 2001 (9/11) terrorist attacks. Saliva was collected by mail from 711 respondents (European American subsample n = 463) of a large national probability sample of 2,729 adults. Respondents completed web-based assessments of pre-9/11 mental and physical health, acute stress 9 to 23 days post-9/11, PTS symptoms, and social constraints on disclosure regarding fears of future terrorist attacks 2-3 years post-9/11. Social constraints were positively associated with PTS symptoms 2-3 years post-9/11. The triallelic 5-HTTLPR genotype was not directly associated with PTS symptoms, but it interacted with social constraints to predict PTS symptoms 2-3 years post-9/11: Social constraints were more strongly associated with PTS symptoms for individuals with any s/lg allele than for homozygous la/la individuals. Constraints on disclosing fears about future terrorism moderate the 5-HTTLPR genotype-PTS symptom association even when indirectly exposed to collective stress.