Introduction
Mental health inequalities across racial and ethnic groups are large and unjust in many countries, yet these inequalities remain under-researched, particularly in low- and middle-income countries such as Brazil. This study investigates racial and socioeconomic inequalities in primary healthcare utilisation, hospitalisation, and mortality for mental health disorders in Rio de Janeiro, Brazil.

Methods
A cohort of 1.2 million low-income adults from Rio de Janeiro, Brazil with linked socioeconomic, demographic, healthcare use and mortality records was cross-sectionally analysed. Poisson regression models were used to investigate associations between self-defined race/colour and primary healthcare (PHC) utilisation, hospitalisation, and mortality due to mental disorders, adjusting for socioeconomic factors. Interactions between race/colour and socioeconomic characteristics (sex, education level, income) explored if Black and Pardo (mixed race) individuals faced compounded risk of adverse mental health outcomes.

Results
There were 272,532 PHC consultations, 10,970 hospitalisations, and 259 deaths due to mental disorders between 2010–2016. After adjusting for a wide range of socioeconomic factors, the lowest PHC utilisation rates were observed in Black (adjusted rate ratio [ARR]:0.64; 95% CI:0.60–0.68; compared to White) and Pardo individuals (ARR:0.87; 95% CI:0.83–0.92;). Black individuals were more likely to die from mental disorders (ARR:1.68; 95% CI:1.19–2.37; compared to White), as were those with lower educational attainment and household income. In interaction models, being Black or Pardo conferred additional disadvantage across mental health outcomes. The highest educated Black (ARR:0.56; 95% CI:0.47–0.66) and Pardo (ARR:0.75; 95% CI:0.66–0.87) individuals had lower rates of PHC utilisation for mental disorders compared to the least educated White individuals. Black individuals were 3.7 times (ARR:3.67; 95% CI:1.29–10.42) more likely to die from mental disorders compared to White individuals with the same education level.

Conclusion
In low-income individuals in Rio de Janeiro, racial/colour inequalities in mental health outcomes were large and not fully explainable by socioeconomic status. Black and Pardo Brazilians were consistently negatively affected, with lower PHC utilisation and worse mental health outcomes.