Suicide rates are elevated among people with Bipolar Disorder (BD), yet there is limited research on the nature of suicide in this population. Intentional overdose (OD) is a common method of suicide, and the objective of this study was to characterize the specifics of OD suicides in a BD cohort, and compare with non-BD suicides.

Coroner records for all cases of OD suicide in Toronto, Canada over a 10-year period (1998-2007) were examined. Data collected included demographics, psychiatric diagnosis and all substances present at lethal levels determined by the coroner to have caused death. Data analysis focused on comparisons between the BD cohort and non-BD suicides.

Suicide by overdose was recorded in 34 people with BD (61.8% female) and 343 people without BD (46.9% female). There were numerous differences between the BD and non-BD suicide cohorts. The BD suicide group was younger, more likely to have made a prior suicide attempt, less likely to have a comorbid medical condition, and more likely to overdose on mood stabilizers or antipsychotics. Carbamazepine was the most frequently identified lethal substance among BD suicides (20.6%), with next most common being diphenhydramine (14.7%) and codeine (14.7%). Lithium was found at lethal levels in only one BD suicide (2.9%) and 3 non-BD suicides (0.9%).

Key differences exist between BD and non-BD groups who suicide by OD, including the types of ingested medications. Improving our understanding of suicide in people with BD will ultimately aid in development of effective, targeted prevention strategies.