State dependent gene-environment interaction: Serotonin transporter gene-child abuse interaction associated with suicide attempt history among depressed psychiatric inpatients

Background: The serotonin transporter gene polymorphism (5HTTLPR) and child abuse history have been associated with an increased suicide risk for general population, but such association is not clear among psychiatric depressed inpatients. Methods: A chart review identified 422 depressed inpatients genotyped for 5HTTLPR. Child abuse and suicide attempt history were recorded. The relationship between 5HTTLPR, child abuse, and suicide attempts were analyzed. Results: There was a significant relationship between 5HTTLPR and history of suicide attempt (the long/long versus the short carriers, 47.9% versus 31.8%, p=0.0015). There was also a significant main effect from child abuse history (abused versus not abused, 45.1% versus 28.6%, p=0.0001). The likelihood ratio test showed a significant result for the l/l genotype group with child abuse history (odds ratio 4.11, χ2 = 23.5, p<0.0001). No significant result was obtained from other groups. Limitations: This is a retrospective study based on chart review. Replication with more standardized research setting for measurements of child abuse history and suicide attempt history is needed. The rs25531 variant among a long allele (long-A and long-G) of 5HTTLPR was not genotyped. Conclusions: In addition to the direct effect from 5HTTLPR and child abuse history, an interaction between the 5HTTLPR gene and child abuse history influenced psychiatric profiles of depressed inpatients. Contrary to the widely recognized reactivity associated with the short allele, our patients with the l/l genotype and child abuse history showed significantly severer psychiatric pathology than short carriers with child abuse history.