Association between low‐activity serotonin transporter genotype and heroin dependence: Behavioral and personality correlates

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Abstract
In previous studies, serotonin (5‐HT) system disturbance was found involved in a variety of behavioral disorders, psychopathologies, and substance use disorders. A functional polymorphism in the promoter region of the human serotonin transporter gene (5‐HTTLPR) was recently identified and the presence of the short (S) allele found to be associated with a lower level of expression of the gene, lower levels of 5‐HT uptake, type 2 alcoholism, violence and suicidal behavior. In the present study, 101 heroin addicts (males, West European, Caucasians) and 101 healthy control subjects matched for race and gender, with no history of substance use disorder, have been genotyped. Aggressiveness levels were measured in both heroin addicts and controls utilizing Buss‐Durkee‐Hostility‐Inventory (BDHI). Data about suicide attempt and violent criminal behavior in subject history have been collected. The short–short (SS) genotype frequency was significantly higher among heroin dependent individuals compared with control subjects (P = 0.025). The odds ratio for the SS genotype versus the long–long (LL) genotype frequency was 0.69, 95% Cl (0.49–0.97), when heroin addicts were compared with healthy controls. The SS genotype frequency was significantly higher among violent heroin dependent individuals compared with addicted individuals without aggressive behavior (P = 0.02). BDHI mean total scores and suspiciousness and negativism subscales scores were significantly higher in SS individuals, in comparison with LL subjects, among heroin addicts. No association was found between SS genotype and suicide history. Our data suggest that a decreased expression of the gene encoding the 5‐HTT transporter, due to “S” promoter polymorphism, may be associated with an increased risk for substance use disorders, particularly in the subjects with more consistent aggressiveness and impulsiveness.