Abstract
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.