An α-synuclein gene (SNCA) polymorphism moderates the association of PTSD symptomatology with hazardous alcohol use, but not with aggression-related measures

•We genotyped the polymorphism SNCA rs356195 in 138 European Americans (EAs).•EAs reported their alcohol use, alcohol-aggression expectancies, and aggression.•We also diagnosed probable PTSD based on participant self-report.•SNCA moderated the association of PTSD symptomatology with hazardous alcohol use.•Variations in SNCA may increase risk of PTSD-related excessive drinking.

Posttraumatic stress disorder (PTSD) often precedes comorbid substance use disorder and has been associated with aggression. Prior research has evidenced that alcohol use and other externalizing behaviors share genetic factors with PTSD; however, few studies have examined if specific genes are associated with externalizing behaviors in PTSD. The purpose of the current study was to investigate whether an α-synuclein gene polymorphism (SNCA rs356195) moderates the association of PTSD symptomatology with externalizing behaviors. We examined the separate and combined effects of PTSD symptomatology and SNCA rs356195 on alcohol- and aggression-related measures in nonclinical participants (N = 138 European Americans; 15 diagnosed with probable PTSD). Probable PTSD status and SNCA were both associated with externalizing measures. SNCA also moderated the association of PTSD symptomatology with hazardous alcohol use, but not with aggression-related measures. Current findings suggest that variations in SNCA may increase the likelihood that PTSD symptomatology results in excessive alcohol use.