Characteristics of included studies (n = 328).

Background and objectivesTransgender and gender diverse (trans) health research has grown rapidly, highlighting the need to characterize the scientific evidence base. We conducted a systematic review of peer-reviewed research on disease burden and correlates in trans adolescents and adults over a 20-month period to identify knowledge gaps and assess methodological characteristics including measurement of gender identity, community engagement, and study quality.Data sources, eligibility criteria, and synthesis methodsWe searched seven databases using terms related to (a) transgender populations and (b) health or disease. Eligible studies were in English, French, or Spanish and reported original quantitative data on mental health or substance use conditions, infectious diseases, or non-communicable conditions in at least 25 trans individuals aged 15+. Quality assessment was performed in duplicate on a 10% sample of articles and findings were summarized using narrative synthesis.ResultsThe 328 included studies were conducted in 45 countries, with most from North America (54%) and limited research from South Asia (3%), Sub-Saharan Africa (3%), and the Middle East and North Africa (2%). Most studies used cross-sectional designs (73%) and convenience sampling (65%). Only 30% of studies reported any form of community engagement. Mental health and substance use disorders were the most studied area (77% of studies) and non-communicable conditions the least (16%). Available data indicated that trans populations experience high disease burden with considerable heterogeneity within and across settings. Of 39 articles assessed for quality, 80% were rated as fair, 18% as poor, and 3% as good quality.Conclusions and implicationsGeographic, gender-specific, and topical gaps remain in trans health, but we found more research from African countries, with transmasculine people, and on non-communicable conditions than previous syntheses. Areas for growth in trans health research include community engagement, non-binary health, chronic and age-related conditions, and health determinants.RegistrationPROSPERO CRD42021234043.