Introduction: Psychiatric disease is overlooked in drug users. Patients with both drug abuse and a psychiatric disease – dual diagnosis – suffer decreased compliance to treatment and decreased life expectancy compared with single-diagnosis patients. Identifying the patients among ­either drug addicts or mentally ill patients is difficult.

Methods: All drug addicts autopsied at the Department of Forensic Medicine, University of Copenhagen, Denmark, in the years 1992, 2002 and 2012 were included. The group was divided into two subpopulations of possible dual diagnosis patients either according to police reports stating mental illness or to psychotropics found in the toxicology screening after autopsy.

Results: We found a rise in possible mental illness in both subpopulations in the study period. Drug addicts with psychotropics in the blood at the time of death increased from 3.1% in 1992 to 48.1% in 2012, and this group was significantly younger at the time of death than those without ­psychotropics in the blood. 


Conclusion: Suspected dual diagnosis patients have increased in number. They die earlier than their drug addict counterparts. Methadone remains the leading cause of death in all subpopulations. Possible causes are misuse of treatment and/or illegally bought methadone, wrongly ­assigned cause of death due to unknown tolerance and/or polydrug toxicity in combination with psychotropic medicine.