Introduction & Objective: There are several close links between substance dependency and mental disorders. Many people who regularly abuse drugs are also diagnosed with psychiatric disorders and vice versa. The high prevalence of this comorbidity has been documented in several studies, although most of the research has been carried out in only a few countries and the cultural validity of the data is unknown. Thus the aim of this study was the comparative investigation of mental disorders in drug dependent and non drug dependent persons in city of Hamadan.

Materials & Methods: This study was a descriptive comparative research. 106 men aged 18 to 51 who sought treatment at addiction rehabilitation department of Hamadan were recruited in this study. Also 106 men in the same age range were matched with the first group. Data were collected through structured clinical interview for DSM-IV-TR and SCL 90-R questionnaire. Data were analyzed using t-test and correlation coefficient test.

Results: The rate and severity of mental disorders in 9 studied Categories of disorders—phobia, anxiety, somatization, psychotism, depression, paranoid thoughts, aggression, interpersonal sensitivity and obsession-compulsion—were significantly higher among the addicts than the normal group.The level of severity was higher in depression, paranoid thoughts and interpersonal sensitivity than the other disorders. 63.5% of addicts suffered from some psychological disorders while the figures for no addicts were 28.8%. The prevalence of co-morbid psychiatric disorders varied with the pattern of addicts.

Conclusion: This study showed that persons with substance dependence display more signs of psycho pathology and mental disorders in comparison with non- substance dependent people.