Alcohol and cannabis use and mortality in people with schizophrenia and related psychotic disorders

Abstract

The impact of co-morbid substance use on mortality is not well studied in psychotic disorders. The objective of this study was to examine the impact of substance use on mortality in people with psychotic disorders and alcohol and/or drug use. We examined the rate of substance use and the risk of substance use on mortality risk over a 4-10 year period in 762 people with psychotic disorders. Deceased patients were identified from the Social Security Death Index and the Maryland Division of Vital Records. Substance use was defined as regular and heavy use or abuse or dependence. Seventy seven percent had co-morbid lifetime substance use, with co-morbid cannabis and alcohol use occurring most commonly. Out of 762 subjects, 62 died during follow up. In a Cox model, predicted mortality risk was higher in age group 35-55 compared to <35 years and in males, but reduced in cannabis users. Overall five- (3.1% vs 7.5%) and ten-year mortality risk (5.5% vs. 13.6%) was lower in cannabis users than in non-users with psychotic disorders (p = 0.005) in a survival model. Alcohol use was not predictive of mortality. We observed a lower mortality risk in cannabis-using psychotic disorder patients compared to cannabis non-users despite subjects having similar symptoms and treatments. Future research is warranted to replicate these findings and to shed light on the anti-inflammatory properties of the endocannabinoid system and its role in decreased mortality in people with psychotic disorders.

Figure 1

Time to death in alcohol users vs. alcohol non-users by age group. Kaplan-Meier Estimates of Cumulative Probability of All-Cause Death by Years of Follow-up, Age and Alcohol use. Log-rank test: χ²=12.7, df=3, p=0.005 <35 years alcohol user N=195 35–55 years alcohol user N=283 <35 years alcohol non-user N=101 35–55 years alcohol non-user N=183

Figure 2

Time to death in cannabis users vs. cannabis non-users by age group. Kaplan-Meier Estimates of Cumulative Probability of All-Cause Death by Years of Follow-up, Age and Cannabis use. Log-rank test: χ²=17.5, df=3, p=0.0006 <35 years cannabis user N=152 35–55 years cannabis user N=143 <35 years cannabis non-user N=144 35–55 years cannabis non-user N=323