The risk of suicide is increased in people with substance use disorders (SUD), but differences in both prevalence and risk exist between the SUDs. This study aimed to examine overall and gender-specific suicide rates and population-attributable fractions in patients diagnosed with different specific SUDs.
We identified individuals registered with a diagnosis of SUD recorded during the last year before they died in suicide between 1.1.2010 and 31.12.2021 based on a linkage between the Norwegian Cause of Death Registry and the Norwegian Patient Registry. We classified the specific types of SUD into alcohol (F10), opiate (F11), cannabis (F12), sedative and hypnotics (F13), other (F14-F16), and multiple substance use disorders (F19) by the last registered SUD. Aggregate data on the number of patients treated with different SUDs were retrieved from the Norwegian Patient Registry and Statistics Norway. We estimated the total and gender-specific suicide rates and the population-attributable fraction (PAF).
Of all patients who had died during contact or within one year after their last contact with specialized mental health or addiction services (N= 3828), 1 258 patients (14.9 %), 842 (14.2 %) men and 406 (16.5 %) women, had received a diagnosis of substance use disorder, corresponding to a suicide rate of 222.2 per 100,000 patient-years. In men, the highest age-adjusted suicide rate was found in patients with alcohol (297.0 (254.2-368.2)) and sedative and hypnotic use disorder (237.6 (140.3-411.4)). In women, the highest age-adjusted suicide rate was in patients with multiple substance (412.2 (253.4-671.3)) and alcohol use disorders (335.1 (269.1-425.7)). The SUD with the highest PAF were alcohol use disorders (6,0 %) in both men (4.5 %) and women (6.6 %), followed by multiple substance use disorders (2.8 %).
Suicide rates differed between people diagnosed with different SUDs, with alcohol, sedative, hypnotic, and multiple substance use disorders having the highest suicide rates. Comparable suicide rates were found in men and women across most of the substance use disorders. Alcohol use disorders had the largest prevention potential of the SUDs. This study only included individuals in SUD treatment, which limits the generalizability of the PAF to a broader population of individuals who use substances. These findings imply that public health and clinical policies for preventing suicide in people with substance use disorders are important areas to strengthen.