Explaining the gaps in psychological distress and suicidal behaviours between non-Indigenous and Indigenous adults living off-reserve in Canada: a cross-sectional study

BACKGROUND: Indigenous people are disproportionately affected by mental health issues in Canada. We investigated factors underlying the difference in psychological distress and suicidal behaviours between non-Indigenous and Indigenous populations living off-reserve in Canada. METHODS: We conducted a cross-sectional study using data from the 2012 Canadian Community Health Survey - Mental Health. Respondents were aged 18 years and older. We measured the variation in psychological distress (10-item Kessler Psychological Distress Scale scores, ranging from 10 [no distress] to 50 [severe distress]) and the prevalence of lifetime suicidal ideation and suicide plan between the Indigenous and non-Indigenous populations and explained these differences using the Blinder-Oaxaca approach. RESULTS: The overall response rate for the survey was 68.9%, comprising 18 300 respondents (933 Indigenous and 17 367 non-Indigenous adults). We found lower mean psychological distress scores among non-Indigenous people than among Indigenous people (15.1 v. 16.1, p < 0.001) and a lower prevalence of lifetime suicidal ideation (9.2% v. 16.8%, p < 0.001) and plan (2.3% v. 6.8%, p < 0.001). We found that if socioeconomic status among Indigenous people were made to be similar to that of the non-Indigenous population, the differences in mean psychological distress scores and prevalence of lifetime suicidal ideation and suicide plan would have been reduced by 25.7% (women 20.8%, men 36.9%), 10.2% (women 11.2%, men 11.9%) and 5.8% (women 7.8%, men 8.1%), respectively. INTERPRETATION: Socioeconomic factors account for a considerable proportion of the variation in mental health outcomes between non-Indigenous and Indigenous populations in Canada. Improving socioeconomic status among Indigenous people through plans like income equalization may reduce the gap in mental health outcomes between the 2 populations in Canada.