Psychosis prevalence studies in the OECD: a scoping review and recommendations for psychosis prevalence research in Aotearoa New Zealand

Background In Aotearoa New Zealand, there is limited quality and up-to-date national psychosis prevalence data to guide service provision. Planned studies must account for socio-cultural and historical context of Aotearoa New Zealand. Method and purpose To inform Aotearoa New Zealand research, we first conducted a scoping review of psychosis prevalence studies in OECD and Pacific countries. The aims of the scoping review were to describe: (1) target populations and sampling frames, (2) psychosis measures, and (3) additional socio-demographic and contextual measures including ethnicity/Indigeneity. Following the scoping review, findings were critically synthesised against authors’ local expertise to inform recommendations for Aotearoa New Zealand. Results One hundred and thirty psychosis prevalence studies (18 child/youth; 112 adult studies) were identified, mostly in general populations, followed by justice, unhoused/temporarily housed, and psychiatric inpatients. Common screening instruments were the Mini-International Neuropsychiatric Interview (MINI), and the Composite International Diagnostic Interview (CIDI). Few studies had the primary aim of estimating psychosis prevalence; most included studies estimated psychosis prevalence as part of broader research aims. Sociodemographic factors and other contextual factors were commonly reported. However, reporting practices regarding ethnicity, and in particular Indigeneity, are limited: only 21/130 total studies (16.2%) report prevalence stratified by ethnicity. Only 14 studies reported inclusion of Indigenous Peoples. Conclusions Due to methodological challenges, psychosis prevalence studies often use incomplete, biased population sampling frames, and infrequently report ethnicity and Indigeneity. Despite limitations, robust psychosis prevalence data are needed. We outline recommendations for doing so in Aotearoa New Zealand child/youth and adult populations.