Abstract
BACKGROUND: Indigenous peoples in Canada have high rates of psychological distress and suicide. We sought to assess the socioeconomic inequalities in psychological distress and suicidal behaviours, and the factors that explain them within Indigenous peoples living off-reserve.
METHODS: Using the nationally representative 2012 Aboriginal Peoples Survey collected from Indigenous adults living off-reserve in Canada, we measured income-related inequalities in psychological distress (measured on the 10-item Kessler Psychological Distress Scale) and suicidal behaviours (suicidal ideation and suicide attempt) and identified factors contributing to these inequalities using the concentration index (C) approach.
RESULTS: Among 14 410 individuals representing 600 750 Indigenous adults (aged ≥ 18 yr) living off-reserve in Canada, the mean score of psychological distress was 16.1; 19.4% reported lifetime suicidal ideation and 2.2% reported a lifetime suicide attempt. Women had higher psychological distress scores (mean score 16.7 v. 15.2, p < 0.001), and prevalence of suicidal ideation (21.9% v. 16.1%, p < 0.001) and suicide attempts (2.3% v. 2.0%, p = 0.002) than men. Poorer individuals disproportionately experienced higher psychological distress (C = −0.054, 95% confidence interval [CI] −0.057 to −0.050), suicidal ideation (Cn = −0.218, 95% CI −0.242 to −0.194) and suicide attempts (Cn = −0.327, 95% CI −0.391 to −0.263). Food insecurity and income, respectively, accounted for 40.2% and 13.7% of the psychological distress, 26.7% and 18.2% of the suicidal ideation and 13.4% and 7.8% of the suicide attempts concentrated among low-income Indigenous peoples.
INTERPRETATION: Substantial income-related inequalities in psychological distress and suicidal behaviours exist among Indigenous peoples living off-reserve in Canada. Policies designed to address major contributing factors such as food insecurity and income may help reduce these inequalities.
Worldwide, Indigenous populations have high rates of suicide and psychological distress, the latter characterized by psychological and physiologic symptoms of anxiety and depression.1–3 Suicide is a major cause of death among First Nations, Métis and Inuit peoples,4 the 3 distinct Indigenous groups in Canada. Suicide rates among Indigenous peoples, when considered collectively, are 2 to 3 times higher than among non-Indigenous Canadians.5 Rates of suicide and distress vary considerably across the Indigenous groups. During the period between 1991 and 2001, the Indigenous to non-Indigenous suicide mortality rate ratio was 1.60 for Métis men, 0.85 for Métis women, 1.66 for status First Nations men and 1.86 for status First Nations women.6 Suicide rates among the Inuit, which are among the highest in the world, are up to 10 times higher than the overall rate for Canada.5,7,8 Suicide led to life expectancy losses of 4.8 years for men and 1.2 years for women in Inuit Nunangat in 1999–2003.9 Suicide rates are higher among First Nations peoples living on-reserve than among Indigenous peoples living off-reserve. 10 The rate ratios for potential years of life lost owing to suicide among status First Nation men living on- and off-reserve compared with non-Indigenous men (women) were 2.88 (3.71) and 1.11 (0.76), respectively.11 Furthermore, except for Métis men, suicidal thoughts among Indigenous peoples are more common than among non-Indigenous Canadians.12
Historical and ongoing experiences associated with colonization accompanied by inequities in income, employment opportunities, housing and food security, among other factors, have resulted in pervasive health problems among Indigenous peoples.4,13–21 Indigenous populations have the poorest health outcomes in Canada, often similar to those of populations in developing countries.18
Income has been shown to be a main determinant of health among both Indigenous22 and the general Canadian populations. 23 Recent evidence points to a particularly strong income-related gradient in mental health outcomes compared with most other health outcomes.24 The role of income may be especially important given persistently lower incomes among Indigenous populations compared with non-Indigenous populations, with a gap of 25% in 2015 and little improvement since 2005.25 There is scant literature on socioeconomic inequalities in mental health within Indigenous peoples in Canada, despite considerable variations in collective histories, present-day circumstances and cultures.
Using data from the 2012 Aboriginal Peoples Survey, we quantified the extent of and factors accounting for income-related inequalities in psychological distress and suicidal behaviours among status First Nations, non-status First Nations, Métis and Inuit peoples living off-reserve in Canada.
Methods
Sample
We used data from the confidential master files of the 2012 Aboriginal Peoples Survey conducted by Statistics Canada. A large cross-sectional survey, with a response rate in 2012 of 76%,26 the Aboriginal Peoples Survey collects detailed data on the social and economic conditions (e.g., education, employment, health, language, income, housing and mobility) from Indigenous peoples aged 6 years and older who are living in private dwellings, excluding those living on Indian settlements and reserves and in specific First Nations communities in the Northwest Territories and Yukon.26 Data from survey participants were adjusted to represent Indigenous adults living off-reserve in Canada using bootstrapped weights, as per guidelines from Statistics Canada’s Research Data Centres.27
Variables
Mental health outcome variables
The outcome variables included psychological distress, lifetime suicidal ideation and lifetime suicide attempt. The 10-item Kessler Psychological Distress Scale (K10) (Appendix 1A, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.181374/-/DC1)28 was used to measure nonspecific psychological distress, composed of items assessing psychological and physiologic symptoms of anxiety and depression. Total scores of the K10 range from 10 (no distress) to 50 (severe distress). Studies have shown that the K10 is psychometrically valid and appropriate for use in Indigenous populations living off-reserve in Canada.28–31 The Aboriginal Peoples Survey also asked questions related to suicidal behaviours, from which we created 2 binary variables of suicidal behaviour: lifetime suicidal ideation and suicide attempt.
Socioeconomic position variables
We used the natural log of equivalized household income (i.e., household income divided by the square root of household size)32 as a proxy of socioeconomic status.
Explanatory variables
The decomposition analysis included variables known to be associated with mental health outcomes in Indigenous populations33– 41 and available in the Aboriginal Peoples Survey. These included 3 demographic variables (sex [male, female], age [continuous] and marital status [single, married, divorced or widowed]), and cultural group (status First Nations, non-status First Nations, Métis, Inuit); 6 socioeconomic variables (natural log of equivalized household income, education [≤ grade 8, grades 9–10, grade 11–secondary completed, some postsecondary, postsecondary degree/diploma], employment status [employed, not in the labour force, unemployed], household crowding [rooms per capita ≤ 2, > 2 to 4, > 4]; housing maintenance [regular, minor or major maintenance needed]; food security [high, low, very low]); 2 behavioural variables (regular drinker, daily tobacco use); 2 social connectedness variables (strong extended family ties, no one to turn to for support); 4 cultural engagement and language variables (clothing or footwear; art craft, hunting, fishing or trapping; plant gathering; speaking Indigenous language); and 2 geographic variables (urbanicity [rural, small population centre, medium population centre, urban], region [Atlantic provinces, Quebec, Ontario, Manitoba, Saskatchewan, Alberta, British Columbia, territories]). Appendix 1B reports the definitions and descriptive statistics of the variables used in the study.
Statistical analysis
The concentration index (C)42 was used to quantify income-related inequalities in mental health outcomes. The C is computed based on the concentration curve, which depicts the cumulative percentage of the population ranked by ascending order of a socioeconomic status variable (e.g., income), on its x-axis, against the cumulative percentage of a health outcome (e.g., psychological distress score). The C is calculated as twice the area between the diagonal (the perfect equality line) and the concentration curve.43 The value of C varies from −1 to 1, with 0 indicating perfect equality.44 Because 2 of our outcome variables were binary (lifetime suicide ideation and attempt), the normalized concentration index (Cn) was used for these outcomes.45 A negative (positive) value of the C and Cn indicate that the health outcome is disproportionately concentrated among individuals with low (high) socioeconomic status.
The C and Cn were decomposed to identify the contributions of a set of k explanatory variables to income-related inequality in each of the health-outcome variables. The decomposition of the C and Cn is based on the regression analysis of the association between the outcome variable and a set of k explanatory variables. 46 The negative contribution of a factor to the Cn suggests that income-related distribution of the factor (i.e., the Ck) and the association between the factor and health outcomes increase the concentration of health outcome among the poor (a positive contribution would increase the concentration of the health outcome among the rich).44,46 Appendix 1C provides a detailed description of the C and Cn and the decomposition of these 2 indexes. The F and χ2 statistics were used to test the differences among covariates for continuous (i.e., psychological distress) and categorical (i.e., suicidal ideation and suicide attempt) variables, respectively. We used bootstrap weights provided by Statistics Canada in the analyses to obtain estimates that are representative of Indigenous populations living off-reserve in Canada and to take into account the complex survey design using the SVY command47 in Stata 14.48 We considered p < 0.05 statistically significant.
Ethics approval
We accessed the Aboriginal Peoples Survey through Statistics Canada’s Atlantic Research Data Centre. Data accessed through the Research Data Centres, which follow strict disclosure protocols according to the Statistics Act, are exempt from research ethics board review based on the Tri-Council Policy Statement: Ethical Conduct for Research Involving Humans (TCPS2) article 2.2 (a).
Results
Prevalence of psychological distress and suicidal behaviours
The Aboriginal Peoples Survey included information on 28 410 respondents. After we excluded 10 550 individuals aged less than 18 years and with multiple Indigenous identities, and 3450 missing values in outcome or explanatory variables, our final sample consisted of 14 410 individuals, representing 600 750 Indigenous people living off-reserve in Canada (Table 1).
The mean distress score among Indigenous peoples was 16.1 for both sexes, 15.2 for men and 16.7 for women (p < 0.001). The prevalence rates of lifetime suicidal ideation and suicide attempt among Indigenous peoples in 2012 for both sexes were 19.4% (men: 16.1%; women: 21.9%, p < 0.001) and 2.2% (men: 2.0%; women: 2.3%, p = 0.002), respectively (Tables 2 and 3).
The mean distress score varied (p < 0.001) among the 4 Indigenous cultural groups, with Inuit having the lowest mean distress score (total: 15.4; men: 14.6; women: 16.0) and non-status First Nations having the highest mean distress score (total: 16.8; men: 15.6; women: 17.7) (Table 2). There was also a significant variation in the prevalence of suicidal ideation (p < 0.001) and suicide attempt (p < 0.001) among the 4 Indigenous cultural groups, with Métis having the lowest rates of suicidal ideation (total: 17.5%; men: 13.8%; women: 20.5%) and suicide attempt (total: 1.7%; men: 1.2%; women: 2.2%), and Inuit having the highest rates of suicidal ideation (total: 22.7%; men: 20.7%; women: 24.3%) and suicide attempt (total: 3.2%; men: 1.6%; women: 4.5%). The prevalence of lifetime suicide attempt was not different between Métis and status and non-status First Nations women (Table 3).
Income-related inequalities in psychological distress and suicidal behaviours
The negative values of the C for psychological distress (−0.054, 95% confidence interval [CI] −0.057 to −0.050) and the Cn for lifetime suicidal ideation (−0.218, 95% CI −0.242 to −0.194) and lifetime suicide attempt (−0.327, 95% CI −0.391 to −0.263) suggest that these mental health outcomes are disproportionately concentrated among those with lower income. Income-related inequality in psychological distress was marginally greater among women (C = −0.055, 95% CI −0.060 to −0.050) than men (C = −0.046, 95% CI −0.051 to −0.040), whereas income-related inequalities in suicide attempts were higher among men (Cn = −0.462, 95% CI −0.562 to −0.362) than women (Cn = −0.236, 95% CI −0.320 to −0.152). For both men and women, income-related inequality in psychological distress was highest among status First Nations (C = −0.069, 95% CI −0.082 to −0.057) and lowest among Inuit (C = −0.039, 95% CI −0.048 to −0.030). Status First Nations men had the highest income-related inequalities in lifetime suicidal ideation (Cn = −0.378, 95% CI −0.496 to −0.260) and suicide attempt (Cn = −0.629, 95% CI −0.868 to −0.390) among Indigenous male cultural groups. Among women, income-related inequalities in suicidal behaviours were highest among Métis (suicidal ideation: Cn = −0.215, 95% CI −0.264 to −0.166; suicide attempt: Cn = −0.269, 95% CI −0.407 to −0.131) and lowest among Inuit (suicidal ideation: Cn = −0.153, 95% CI −0.226 to −0.080; suicide attempt: Cn = −0.126, 95% CI −0.278 to −0.026) (Table 4).
Determinants of Income-related inequalities in psychological distress and suicidal behaviours
The decomposition analyses showed food insecurity as the most important factor contributing to income-related inequalities in the 3 mental health outcomes among men and women (Table 5). Food insecurity accounted for 40.2% (men: 38.4%; women: 42.9%), 26.7% (men: 21.4%; women: 32.2%) and 13.4% (men: 3.2%; women: 20.2%) of the income-related inequalities in psychological distress, lifetime suicidal ideation and lifetime suicide attempt, respectively. The negative contribution of food insecurity to the C and Cn suggests that food insecurity increases the concentration of mental health outcomes among low-income Indigenous peoples in Canada.
Moreover, the income variable itself contributed negatively to income-related inequalities in psychological distress and lifetime suicidal ideation for men and women. Income accounted for 13.7% (men: 12.9%; women: 14.0%) of income-related inequalities in psychological distress, 18.2% (men: 20.1%; women: 17.6%) of those in lifetime suicidal ideation, and 7.9% of those in suicide attempt among men. Employment status explained 13.5% (men: 11.1%; women: 14.9%) of income-related inequalities in psychological distress and 7.2% (men: 3.1%; women: 7.9%) of income-related inequalities in suicide attempt. Unexplained variables accounted for a residual 5.5% (men: 16.3%; women: −0.5%) of income-related inequalities in psychological distress, but 20.3% (men: 31.7%; women: 12.8%) of income-related inequalities in suicidal ideation and 63.0% (men: 79.7%; women: 63.7%) of income-related inequalities in suicide attempt.
Interpretation
We showed high prevalence rates of psychological distress, lifetime suicidal ideation and suicide attempt among Indigenous peoples living off-reserve in Canada in 2012. Income-related inequality in psychological distress was higher among women than men, while income-related inequalities in suicidal behaviours were higher among men. Across the 4 groups compared, income-related inequalities in mental health outcomes were greater among status First Nations men and Métis women.
The results of our study are consistent with those of an analysis in Saskatchewan, which showed higher household income to be a protective factor against lifetime suicidal ideation among Indigenous peoples.49 Our results are also consistent with the findings of previous studies examining associations between income and mental health outcomes among non-Indigenous populations. A 2005 study involving 200 low-income African Americans found that life hassles (defined as work and time pressure), social and cultural difficulties, finances, and social acceptability and victimization, were all independently significant risk factors for suicide attempt.50 A case–control study in New York City suggested that suicide decedents were more likely to be younger and reside in communities with high income inequality and low income per capita.51
A complex interplay of biological, social and cultural factors contribute to mental health problems.52 Within this complex interplay, food insecurity is recognized as one of the main factors contributing to the poor mental health outcomes within Indigenous and non-Indigenous populations.53–64 Data from the 2012 Canadian Community Health Survey showed that 28.2% of off-reserve Indigenous households experienced some form of food insecurity in the past year, compared with 12.6% within the overall Canadian population.65 The decomposition results indicated that food insecurity made the largest contribution to the concentration of psychological distress and suicidal behaviours among low-income Indigenous peoples in Canada. Greater food insecurity increases probabilities of poor mental health outcomes, and food insecurity is more prevalent among the poor. The contribution of food insecurity to income-related inequalities in the 3 mental health outcomes was greater among women than men.
Based on our results, addressing food insecurity among low-income Indigenous peoples living off-reserve may potentially reduce a substantial proportion of the observed income-related inequalities in mental health outcomes. Our findings also point to the importance of household income and employment status as contributors to income-related inequalities in the 3 mental health outcomes. The contribution of employment is important because, compared with employed Indigenous peoples, Indigenous peoples who are not in the labour force or are unemployed had higher probabilities of having mental health problems and were generally poorer.
Limitations
Our analyses have several limitations. First, the Aboriginal Peoples Survey does not collect information from individuals living in institutions (e.g., prisons and hospitals) and other collective dwellings (e.g., shelters, rooming houses and group homes), where a disproportionate number of Indigenous people reside. This exclusion omits many Indigenous peoples known to be at high-risk for adverse mental health problems.66,67 Second, we used the lifetime time frame to examine suicidal behaviours in the study to ensure a large enough number of respondents with outcome variables for the analyses. It would be ideal for future studies to have concurrent measures of outcome and explanatory variables. Third, some of the explanatory factors in the decomposition analysis are likely to be endogenous and may lead to unknown bias in the study. For example, endogeneity in the case of smoking behaviour can be due to the impossibility of distinguishing causality (i.e., whether smoking leads to a mental health issue or mental health issues leads to smoking). Fourth, owing to the unavailability of these data in the Aboriginal Peoples Survey, our analyses included limited historical, cultural, and contemporary factors that are likely important determinants of Indigenous health, including the diversity of nations and cultures that exist within First Nations, Inuit and Métis peoples. Fifth, the contributions of the residual component to income-related inequalities in lifetime suicide ideation and attempt were substantial. This suggests that other factors not included in our models affect socioeconomic inequalities in mental health outcomes among Indigenous peoples. This could also be due, in part, to the less-than-optimal specification of the explanatory variables included in our models. Finally, because we used a survey of living individuals, we did not consider completed suicides, which excluded the most severe mental health outcome in our analyses.
Conclusion
We found persistent and substantial income-related inequalities in psychological distress and suicidal behaviours among Indigenous peoples living off-reserve in Canada. Indigenous peoples in Canada have high rates of mental health problems and experience some of the greatest inequalities in social determinants of health.4,19,20 Our findings underscore the need for greater policy attention to socioeconomic inequalities in mental health within Indigenous peoples as well as inequalities in mental health between Indigenous and non-Indigenous people. To address mental health issues faced by Indigenous peoples, policies must address a broader array of social determinants, such as food insecurity, income and employment status.
Acknowledgements
The analyses presented in this paper were conducted at the Statistics Canada’s Atlantic Research Data Centre at Dalhousie University, which is part of the Canadian Research Data Centre Network. The authors thank the Canadian Research Data Centre Network for facilitating the access to the Aboriginal Peoples Survey and the Atlantic Research Data Centre analyst Heather Hobson for her support and assistance. The authors also thank participants at the 52nd Annual Conference of the Canadian Economics Association, the 12th European Conference on Health Economics and the 2018 Canadian Association for Health Services and Policy Research for their comments and suggestions.
Footnotes
Visual abstract available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.181374/-/DC2
Competing interests: Mohammad Hajizadeh, Amy Bombay and Yukiko Asada report grants from the Nova Scotia Health Research Foundation.
This article has been peer reviewed.
Contributors: All authors contributed to the conception and design of the study. Mohammad Hajizadeh performed the statistical analysis and all authors interpreted the results. Mohammad Hajizadeh drafted the manuscript, and Amy Bombay and Yukiko Asada contributed to drafting and revisions. All authors read and approved the final version of the manuscript and agreed to be accountable for all aspects of the work.
Funding: Funding for this research was provided by the Nova Scotia Health Research Foundation Establishment Grant program (grant no. 1017).
- Accepted February 28, 2019.