Acute and Posttraumatic Stress Symptoms in a Prospective Gene × Environment Study of a University Campus Shooting

CONTEXT: The serotonin transporter (SLC6A4) has been associated with several stress-related syndromes including posttraumatic stress disorder (PTSD). The ability to detect meaningful associations is largely dependent on reliable measures of preexisting trauma. OBJECTIVE: To study the association of genetic variants within SLC6A4 with acute and posttraumatic stress symptoms in a civilian cohort with known levels of preexisting trauma and PTSD symptoms collected prior to a shared index traumatic event. DESIGN: Ongoing longitudinal study. SETTING: On February 14, 2008, a lone gunman shot multiple people on the campus of Northern Illinois University in DeKalb, Illinois, killing 5 and wounding 21. As part of an ongoing longitudinal study on that campus, a cohort of female undergraduate students, interviewed prior to the shooting, completed follow-up trauma-related measures including PTSD symptom severity (follow-up survey was launched 17 days postshooting; n = 691). To obtain DNA, salivary samples were collected from a subset of the original study population based on willingness to participate (n = 276). PARTICIPANTS: Two hundred four undergraduate women. MAIN OUTCOME MEASURES: SLC6A4 polymorphisms STin2, 5-HTTLPR, and rs25531 were genotyped in 235 individuals. RESULTS: We found that although the STin2 variant and 5-HTTLPR alone did not associate with increased PTSD symptoms, rs25531 and the 5-HTTLPR multimarker genotype (combined 5-HTTLPR and rs25531) were associated with significantly increased acute stress disorder symptoms at 2 to 4 weeks postshooting (n = 161; P < .05). This association remained significant when controlling for race and for level of shooting exposure (n = 123; P < .007). The association was most robust with the 5-HTTLPR multimarker genotype and avoidance symptoms (P = .003). CONCLUSION: These data suggest that differential function of the serotonin transporter may mediate differential response to a severe trauma. When examined in a relatively homogenous sample with shared trauma and known prior levels of child and adult trauma, the 5-HTTLPR multimarker genotype may serve as a useful predictor of risk for PTSD-related symptoms in the weeks and months following the trauma.