Self-harm, self-poisoning or self-injury, irrespective of the motivation, is a central risk factor for suicide. Still, there is limited knowledge of self-harm among patients with substance use disorders (SUDs) who die by suicide.

We aimed to describe the prevalence of a history of self-harm and identify the factors associated with self-harm, comparing individuals who died by suicide with and without SUDs.

We used data from the Norwegian Surveillance System for Suicide in Mental Health and Substance Use Services, which is based on a national linkage between the Norwegian Cause of Death Registry and the Norwegian Patient Registry, to identify individuals who died by suicide within 1 year after last contact with mental health or substance use services (n = 1140). A questionnaire was retrieved for 1041 (91.3%) of these individuals. We used least absolute shrinkage and selection operator (LASSO) regression to select variables and compared patients with and without SUDs. Conditional selective inference was used to improve 90% confidence intervals and p-values.

The prevalence of self-harm was 55% in patients with SUDs and 52.6% in patients without SUDs. Suicidal ideation (odds ratio 2.98 (95% CI 1.74–5.10)) emerged as a factor shared with patients without SUDs, while personality disorders (odds ratio 1.96 (1.12–3.40)) and a history of violence (odds ratio 1.86 (1.20–2.87)) were unique factors for patients with SUDs.

A history of self-harm is prevalent in patients with SUDs who die by suicide and is associated with suicidal ideation, a history of violence and personality disorders in patients with SUDs.