Bipolar Disorder and Poisoning due to Medicines or Illegal Substances.

Background: Individuals with bipolar disorder face an elevated risk of premature death, often due to external causes such as accidental injuries, self-harm, and substance-related deaths. This study aimed to investigate the incidence of severe poisonings among individuals with bipolar disorder and to examine associated demographic and clinical factors.

Methods: We conducted a cohort study using data from national registers in Finland, measuring hospitalizations and deaths due to poisoning by medicines or illegal substances in 1996-2018. Cox proportional hazards regression models were used to assess associations between predictor variables and poisoning outcomes.

Results: The study population comprised 60,045 individuals aged 15-65 diagnosed with bipolar disorder in 1987-2018. During the study period, 13.1% (N = 7872) of the population experienced at least one poisoning resulting in hospitalization or death. The age-standardized rate of hospitalizations was 50.6 (95% CI, 49.5-51.7) per 1000 person-years and of deaths 1.8 (95% CI, 1.6-2.0) per 1000 person-years. The majority of poisonings leading to hospitalization (59.1%) or death (56.6%) were intentional and caused by pharmaceuticals (hospitalizations, 76.9%; deaths, 63.6%). Additionally, psychoactive narcotics and stimulants were the cause of 26.8% of the poisoning deaths. The strongest risk factors for hospitalization were substance use disorder (adjusted hazard ratio, aHR, 2.75, 95% CI, 2.61-2.90) and a history of suicide attempt (2.70, 2.52-2.88). The risk of poisoning death was most strongly associated with substance use disorder (3.02, 2.60-3.52) and a history of suicide attempt (2.38, 1.94-2.91). Female sex was associated with a higher risk of hospitalization (1.19, 1.14-1.25), but a lower risk of death (0.72, 0.62-0.82).

Conclusion: Individuals with bipolar disorder face a substantial risk of poisoning by medicines or illegal substances, with notable sex differences in hospitalization and death rates. Key risk factors include substance use disorder and a history of suicide attempt.