This study aimed to investigate the prevalence of mental disorders caused drug dependency and substance abuse in hospitalized patients of Farabi Hospital in Kermanshah City. The study method was retrospective descriptive. The research population and statistical sample consisted all of patients with mental disorders and hospitalized drug abuse in Farabi Psychiatric Hospital in 2012 which 359 patients (325 male and 29 female) were selected. Data collection was based on the archived records. Finally, data collected by SPSS software, version 19, using descriptive statistics (frequency, percentage, mean, standard deviation) were analyzed by chi-square test. The mean age of patients with psychiatric disorders was 31.44, which 90.5 of them was male with the education level of primary school to high school (58.8 percent). The highest rate of abused drug was related to Shisha (82.5%). Single people abused drug more than married people. There was not a significant relationship between tramadol, methadone and Shisha, while there was a significant relationship between abuse of opium and heroin. Men aged 26 to 35 had the largest population of drug dependence and psychosis with hallucinations was seen in most cases and the duration of Shisha abuse in most of cases was higher. Since there is a close relationship between mental disorders and drug abuse so it is recommended that by proper and timely diagnosis, effective actions done to treat drug addicts.
