Influence of Baseline Psychiatric Disorders on Mortality and Suicide and Their Associations with Gender and Age in Patients with Methamphetamine Use Disorder

High mortality rates in patients with methamphetamine use disorder (MUD) are well documented. However, the influence of co-occurring psychiatric disorders on the risks of various causes of mortality, especially suicide, has not been elucidated. The objective of this study is to investigate the impacts of co-occurring psychiatric disorders on mortality in patients with MUD and their associations with age and gender. We used the Taiwan National Health Insurance Research Database to construct a population-based cohort of patients with MUD between January 1, 2002, and December 31, 2017. Mortality data were obtained by linking to the National Death Certification Database. All patients were followed up until their death or the end of the study (December 31, 2018), whichever occurred first. The main outcomes and measures are the outcomes were death and the underlying cause of death. In total, 21,809 patients with MUD were included. During a median follow-up time of 6 (interquartile range: 3 ~ 12) years, we recorded 2245 (10.29%) deaths. Patients with MUD were more likely to die from unnatural causes than natural causes, with respective mortality rates of 689 and 665 per 100,000 person-years. MUD patients with co-occurring psychiatric disorders had increased all-cause mortality (adjusted hazard ratio (aHR): 1.6, 95% confidence interval (CI) = 1.47 ~ 1.75), natural mortality (aHR: 1.37, 95% CI = 1.22 ~ 1.55), unnatural mortality (aHR: 1.93, 95% CI = 1.71 ~ 2.19), and suicides (aHR: 2.35, 95% CI = 1.96–2.82) than those without co-occurring disorders. Patients with co-occurring bipolar disorder had the highest risk of suicide, followed by those with depression, schizophrenia, and anxiety disorders. Furthermore, young women (< 25 years old) with MUD who had co-occurring psychotic disorders exhibited a 2.70-fold increase in suicide risk over those who had no co-occurring disorders. Co-occurring psychotic disorders are important factors in mortality and suicide of MUD patients. These results may enhance clinicians’ attention to provide proper treatment and timely interventions for individuals with co-existing MUD and mental disorders.