Background: Bipolar disorder and anxiety disorders are two prominent mental disorders that represent a significant global health challenge. Objective: The Global Burden of Disease Study 2021 (GBD 2021) was employed to evaluate sex differences in the incidence of bipolar disorder (BD) and anxiety disorder (ANX) globally by year, age, and socioeconomic status. Method: We estimated sex-specific incidence of BD and ANX from GBD 2021 globally and in 204 countries and territories from 1990 to 2021. The sociodemographic index (SDI) was used to gauge national socioeconomic development and the Health Organization (WHO) region was used as a division of regions. Differences in age-standardized incidence rates (ASRs) by sex (absolute and relative) and risk ratios (95% confidence interval) were calculated annually and by age. Annual percent change (APC) was calculated by joinpoint regression modeling and linear regression analyses were performed to explore the socioeconomic factors associated with sex differences in incidence. Results: The absolute and relative sex difference in ASRs of BD showed a slight declining trend during 1990 and 2021, with absolute difference decreasing from 2.50 to 1.83, and relative difference decreasing from 1.08 to 1.06; The absolute and relative sex difference in ASRs of ANX showed an increasing trend during 1990 and 2021, with absolute difference increasing from 170.02 to 208.08, and relative difference increasing from 1.35 to 1.36. Worldwide, females had a higher risk of BD and ANX than males in 1990and 2021. The highest Risk ratios of BD and ANX were observed in the European Region in 2021.The greatest relative sex difference of BD was 1.09 in the age group of 30-34. The greatest relative difference of ANX was 1.51 in the age group of 20-24. Relative sex differences of BD and ANX were significantly and positively correlated with SDI (BD, standardized β = 0.27 (95% CI, 0.22 to 0.33), P < 0.001; ANX, standardized β = 0.80 (95% CI, 0.47 to 1.14), P < 0.001). Conclusions: Sex difference in the incidence of anxiety disorders and bipolar disorder have persisted worldwide over the past several decades, and the rates have consistently been higher among females than males. The sex difference in the global incidence of bipolar disorder has shown a slight improvement, but that in the global incidence of anxiety disorders has not been effectively mitigated. The sex difference is even more pronounced at younger ages and in more developed nations. The findings emphasize the significance of sex-specific health policies to reduce sex differences in the incidence of bipolar and anxiety disorders.
