As the serotonin transporter gene (SLC6A4 or 5-HTT) is a key regulator of central serotonergic activity, several association studies between Antisocial Personality Disorder (APD) and the SLC6A4 polymorphisms have been conducted in the last decade. In the present study, the role of both 5-HTTLPR and 5-HTTVNTR polymorphisms of the SLC6A4 gene in APD is investigated. A sample of 147 male inmates was analyzed. APD was assessed by Aluja's Antisocial Personality Disorder Scale, a measure that correlates 0.73 with the dimensional score of DSM-IV APD and 0.62 with factor II of the Psychopathy Checklist-Revised. Inmates presenting both 5-HTTLPR S/S+S/L and 5-HTTVNTR 12/12 had a higher risk of being classified in the APD group (Odds ratio=3.48). The results also showed that the genotype and haplotype distribution was more dissimilar when extreme groups were compared with odds ratios up to 6.50. Our results supported that, in addition to the widely investigated 5-HTTLPR polymorphism, the 5-HTTVNTR polymorphism might be an interesting candidate for association studies with APD. Results also suggested that previous failures to replicate the association between serotonin transporter gene polymorphisms and APD, or similar phenotypes, could have been due to an under-representation of extremely high APD subjects in the samples analyzed.

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