Mortality among male forensic and non-forensic psychiatric patients: matched cohort study of rates, predictors and causes-of-death.

Background: The mortality of forensic psychiatric (FP) patients compared to non-forensic psychiatric (non-FP) patients has been sparsely examined.Methods: We conducted a matched cohort study and compared Danish male FP patients (n = 490) who underwent pre-trial forensic psychiatric assessment (FPA) 1980-1992 and were subsequently sentenced to psychiatric treatment with matched (on year of birth, marital status, and municipality of residence) male non-FP patients (n = 490) and male general population controls (n = 1716). FP and non-FP patients were also matched on major psychiatric diagnostic categories. To determine mortality and identify potential predictors of mortality, we linked nationwide register data (demographics, education, employment, psychiatric admission pattern and diagnoses, cause of death) to study cohorts. Average follow-up time was 19 years from FPA assessment/sampling until death/censoring or 31 December 2010 and risk factors were studied/controlled with Cox proportional hazard analysis.Results: Overall, psychiatric patients had significantly higher mortality compared to matched general population controls (medium to large effects). Among patients, 44% (213) of FP vs. 36% (178) of matched non-FP patients died during follow-up (p = 0.02). When we used Cox regression modeling to control for potential risk factors; age, education, immigrant background, employed/studying at index, length of psychiatric inpatient stay/year, and ever being diagnosed with substance use disorder (SUD), FP patient status was no longer significantly associated with increased mortality, whereas SUD and longer inpatient time per year were independently associated with increased mortality.Discussion: This study suggests that SUD and longer inpatient time per year are independent risk factors for increased mortality in psychiatric patients.