Sex differences in risk factors for suicidality among Japanese substance use disorder patients: Association with age, types of abused substances, and depression

Aim: The aim of this study was to identify risk factors for suicide in Japanese substance use disorder (SUD) patients, adjusting for age and sex, and to examine sex differences in suicide risk among these patients. Methods: A self-reporting questionnaire on age, sex, types of abused substances, current depression, and suicidality was administered to 1420 SUD patients who consecutively visited seven hospitals specializing in SUD treatment during the month of December 2009. Unadjusted/adjusted odds ratios of factors associated with suicidality were calculated for each sex. Results: The multivariate analysis using the total sample identified younger age, female sex, and current depression as risk factors for severe suicidality in SUD patients. The multivariate analysis by each sex demonstrated that younger age and current depression were associated with severe suicidality in male SUD patients. Only current depression was associated with severe suicidality in female patients. Conclusion: Current depression is a risk factor for suicide in SUD patients common in both Western countries and Japan, although in Japanese SUD patients both younger age and female sex were more closely associated with severe suicidality than aspects of SUD. Additionally, young male SUD patients are speculated to have psychosocial features associated with suicidality in common with female SUD patients.