Background: Phenomenon of addiction as one of the social problems has a high prevalence, especially among youth. The aim of the present study was to compare personality traits based on the temperament and character inventory in opiate and stimulant addicts in Tehran.

  Methods: In the present quasi-experimental study, 60 male addicts (30 opiate and 30 stimulant addicts) who referred to addiction treatment centers in the suburbs of Tehran were selected through convenience sampling method and were studied using Temperament and Character Inventory (TCI). The participants were sorted according to their age and education. 

  Results: There was a significant difference between the two groups with regard to harm avoidance, reward dependence, cooperativeness, and self-transcendence traits. Thus, opiate addicts had higher levels of harm avoidance, reward dependence, and cooperativeness, and stimulant addicts had higher levels of self-transcendence. The significance level was set at P<0.01.

  Conclusion: The obtained results showed that there was a significant difference between opiate and stimulant addicts. Opiate addicts gained higher scores, compared with stimulant addicts, in Temperament and Character Inventory variables. The obtained results also showed that stimulant addicts were suffering from more severe disorders than opiate addicts. Based on the means of the values of the TCI, personality traits reflecting personality disorders are detectable and predictable in substance abusers. This new understanding is important in the prevention and treatment of addiction.