Association study of a novel functional polymorphism of the serotonin transporter gene in bipolar disorder and suicidal behaviour.

A serotonin transporter gene linked polymorphic region (5-HTTLPR) has been investigated in several genetic association studies, including studies of bipolar disorder (BD) and suicidality. The current study was designed to examine whether the new long (A/G) variant polymorphism of the 5-HTT gene may be associated with the suicide attempts in 305 families with at least one member having BD. No association with history of suicide attempt was found either in the multiallelic HTTLPR (LRS=0.15, df=2, P=0.92), or with the intron 2 variable number tandem repeat (VNTR) polymorphism (LRS=0.87 df=2 P=0.64). When we performed a haplotype analysis, we found no association between suicide attempt and haplotype distribution (LRS=1.84 df=4 P=0.76). These findings suggest that this new polymorphism in the 5-HTT gene may not influence suicidal behaviour in patients with bipolar disorder.