Results from a prospective, register-based cohort study indicate that individuals with severe mental illness who also have a substance use disorder have higher mortality compared with their peers without substance use disorders.
“A better understanding of the potential contribution of substance use disorders to the raised mortality in people with mental illness will provide clues to reduce this excess mortality in these patients. A reduced lifespan by 15 to 20 years in people with mental illness has been previously described, but without adjustment for substance use. Ultimately, this information can guide prevention, detection, and treatment programs for substance use disorders,” Carsten Hjorthøj, PhD, of Copenhagen University Hospital, and colleagues wrote.
Researchers evaluated data from a nationwide register for all individuals with schizophrenia, bipolar disorder or unipolar depression born in Denmark in 1955 or later. The study population included 41,470 individuals with schizophrenia, 11,739 individuals with bipolar disorder and 88,270 with depression. Treatment for substance use disorders, date of death, primary cause of death and education level were assessed.
Individuals with schizophrenia and substance use disorder had a standardized mortality ratio of 8.46 (95% CI, 8.14-8.79), compared with 3.63 (95% CI, 3.42-3.83) among those with schizophrenia without substance use disorder.
Among individuals with bipolar disorder, those with a substance use disorder had a standardized mortality ratio of 6.47 (95% CI, 5.87-7.06) and those without a substance use disorder had a mortality ratio of 2.93 (95% CI, 2.56-3.29).
Individuals with depression and substance use disorder had a standardized mortality ratio of 6.08 (95% CI, 5.82-6.34) vs. 1.93 (95% CI, 1.82-2.05) among those with depression without a substance use disorder.
Among individuals with schizophrenia, all substance use disorders were associated with an increased risk for all-cause mortality, including alcohol (HR = 1.52; 95% CI, 1.4-1.65), cannabis (HR = 1.24; 95% CI, 1.04-1.48) and hard drugs (HR = 1.78; 95% CI, 1.56-2.04).
Only substance use disorders involving alcohol or hard drugs were significantly associated with an increased risk for all-cause mortality among individuals with depression or bipolar disorder.
“Our findings raise the hypothesis that successful treatment of substance use disorders might reduce mortality in people with severe mental illness. Unfortunately, reviews have shown that treating substance use disorders in people with severe mental illness is often not effective. Nonetheless, awareness of substance misuse in people with mental illness could help clinical efforts to reduce excess mortality,” the researchers concluded. – by Amanda Oldt
Disclosure: The researchers report no relevant financial disclosures.