The interactive effect of the serotonin transporter genotype and drug use on suicidal behaviors in patients diagnosed with bipolar disorder.

ABSTRACT

BACKGROUND: Suicide is a public health crisis, accounting for more than 47,000 deaths in the United States annually. Individuals with Bipolar Disorder (BD) are at a disproportionately greater risk of suicidal behaviors. Prior studies indicate the significant role of genotype and drug use individually on suicidal behaviors. We hypothesized that, consistent with the gene X environment (GXE) framework, an interaction between serotonin receptor (5-HTTLPR) gene and drug use would influence suicidal behaviors in BD patients. METHODS: One hundred and fifty BD patients at a public urban behavioral health clinic enrolled. The majority were females (n  104, 69.3%), between 19 and 65 years of age (M  39.5, SD= 10.9), African American (n  110, 73.3%), unemployed (78.7%, n  118) with 32% identifying as homeless (n  48). Measures of current mood symptoms, historic suicidal behaviors, and recent substance use were completed, and buccal swabs collected. A moderation analysis was employed for data analysis. RESULTS: Suicidal behaviors were significantly associated with genotype X drug use interaction (B  0.41, 95%CI= [0.06, 0.77], p= .03) followed by gender (B = 1.92, 95%CI= [0.59, 3.25], p= .005), genotype (B= -1.93, 95%CI= [-3.49, -0.36], p= .02), and employment (B= -1.72, 95%CI= [-3.12, -0.31], p= .02). LIMITATIONS: The relatively small sample size primarily comprised of an indigent urban population may limit generalizability. Drug use and suicide risk measures were self-reported and potentially influenced by social desirability bias. CONCLUSIONS: The 5-HTTLPR plays a moderating role on the association between drug use-suicidal behaviors with a differential impact of short and long alleles.