The dual diagnosis of substance abuse and severe mental illness has been proposed by some authors to highlight the high frequency of such association. Our objectif was to determine the prevalence of dual diagnosis among mentally ill patients and and particularly personality disorder patients. as a secondary purpose, to describe the profile of patient at higher risk to develop dual diagnosis.

683 mentally ill patients were recruited from el Mamoura Psychiatric Hospital, they were assessed by the Arabic version of 6 item K6 scale, those scoring above 13 were submitted to a structured clininical interview SCID-II for personality disorder, urine screening for drugs of abuse and complete history of substance abuse and other medical disciplines.

22% of the sample fulfill the diagnosis of dual diagnosis. 12% of the sample had personality disorder, 57.32% among the later were fulfilling diagnosis of dual diagnosis. Results reveals higher risk for dual diagnosis in patients younger in age, single, low socioeconomic state and low level of education. No difference between different personality disorder subtypes as regarding rate of dual diagnosis.

Double diagnosis is an important issue that needs more focus in mental health services. Awareness of mental health providers about dual diagnosis is highly recommended.