The largest excess mortality risk has been reported for combinations of psychiatric disorders that included substance use disorders.

To study the associations of different non-substance-related in-patient psychiatric diagnoses with all-cause mortality and suicide up to 28 years of age after entering substance use treatment.

National register data on psychiatric hospital admissions and death were combined with the treatment records of over 10 000 individuals in substance use treatment between 1990 and 2009. Cox regression was used to calculate hazard ratios (HRs) with 95% CIs for all-cause and suicide-specific mortality from the time of entering substance use treatment.

Nearly one-third (31.4%; n = 3330) of the study population had died during follow-up or by their 65th birthday, with more than one in ten (n = 385) from suicide. Over half of the study population (53.2%) had undergone psychiatric in-patient care and 14.1% involuntary psychiatric care during the study period. Bipolar disorder and unipolar depression were associated with a 57% (HR 1.57, 95% CI 1.18–2.10) and 132% (HR 2.32, 95% CI 1.21–4.46) increase in risk of suicide, respectively. Involuntary psychiatric care was associated with a 40% increase in risk of suicide (HR 1.42, 95% CI 1.05–1.94).

Severe psychiatric morbidity is common among individuals seeking treatment for alcohol and/or substance use and specifically mood disorders appear to increase the risk of suicide. Treatment service planning needs to focus on integrated care for concomitant substance use and psychiatric disorders to address this risk.