Background & Objectives: The drug addiction has different aspects and leads to the significant clinical damage. It can be related to the biological processes and personality traits such as temperament and character.

Material & Methods: This correlation study assessed relationship between temperament and character features and severity of addiction. Two hundred thirty five prisoners and 50 non prisoners who were drug-dependent individuals were randomly selected from Quchan. Participants replied to the Addiction Severity scale (ASI) and temperament and character features (TCI-125).

Results: The results showed that there was a significant difference between temperament and character features in addicted prisoners and non-prisoners in all subtests of temperament and character features (P<0.01). There was significant difference between prisoners and non-prisoners in severity of drug addiction on all subscales (P<0.01).The scales of novelty seeking and reward dependence have also a significant positive correlation with the severity of addiction (P<0.01). There was also a significant inverse correlation in measures to avoid damage, perseverance as well as natural features (total) (P<0.01). Regression analysis showed that 48.3% of the variance related to addiction severity is explained by temperament and character features (36.7% predicted by temperament and 10.9% by character features) (P<0.001). On the other hand, 15.2% and 12.1% of the variance of addiction severity (total) were explained by the novelty seeking and reward dependence alone, respectively. Only 8.9% of the total addiction severity variance was explained by self transcendence.

Conclusion: Attention to the personality character and severity of addiction can be effective on treatment, harm reduction and drug craving interventions.