The prevalence of depression and anxiety disorders in indigenous people of the Americas: A systematic review and meta-analysis.

Indigenous populations are considered at higher risk of psychiatric disorder but many studies do not include direct comparisons with similar non-Indigenous controls. We undertook a meta-analysis of studies that compared the prevalence of depression and anxiety disorders in Indigenous populations in the Americas with those of non-Indigenous groups with similar socio-demographic features (Registration number: CRD42015025854). A systematic search of PubMed, Medline, PsycInfo, PsycArticles, ScienceDirect, EMBASE, and article bibliographies was performed. We included comparisons of lifetime rates and prevalence of up to 12 months. We found 19 studies (n = 250, 959) from Latin America, Canada and the US. There were no differences between Indigenous and similar non-Indigenous groups in the 12-month prevalence of depressive, generalised anxiety and panic disorders. However, Indigenous people were at greater risk of PTSD. For lifetime prevalence, rates of generalised anxiety, panic and all the depressive disorders were significantly lower in Indigenous participants, whilst PTSD (on adjusted analyses) and social phobia were significantly higher. Results were similar for sub-analyses of Latin America, Canada and the US, and sensitivity analyses by study quality or setting (e.g. health, community etc.). Risk factors for psychiatric illness may therefore be a complex interaction of biological, educational, economic and socio-cultural factors that may vary between disorders. Accordingly, interventions should reflect that the association between disadvantage and psychiatric illness is rarely due to one factor. However, it is also possible that assessment tools don't accurately measure psychiatric symptoms in Indigenous populations and that further cross-cultural validation of diagnostic instruments may be needed too.