BackgroundWomen and gender-diverse individuals face disproportionate socioeconomic burden during COVID-19. We compared mental health symptom changes since pre-COVID-19 by sex or gender.MethodsWe searched MEDLINE, PsycINFO, CINAHL, EMBASE, Web of Science, China National Knowledge Infrastructure, Wanfang, medRxiv, and Open Science Framework December 31, 2019 to March 22, 2021 for studies that reported mental health outcomes prior to and during COVID-19 by sex or gender. We conducted restricted maximum-likelihood random-effects meta-analyses.ResultsAll 11 included studies (9 unique cohorts) compared females or women to males or men; none included gender-diverse individuals. Continuous symptom change differences were not statistically significant for depression (standardized mean difference [SMD]= 0.15, 95% CI - 0.09 to 0.39; 3 studies, 4,159 participants; I2=77%) and stress (SMD= -0.09, 95% CI -0.21 to 0.02; 3 studies, 1,217 participants; I2=0%), but anxiety (SMD= 0.14, 95% CI 0.01 to 0.26; 3 studies, 4,028 participants; I2=34%) and general mental health (SMD= 0.15, 95% CI 0.12 to 0.18; 2 studies, 15,590 participants; I2=0%) worsened more among females or women than males or men. There were no significant differences in changes in proportion above a cut-off: anxiety (difference= 0.00, 95% CI -0.01 to 0.02; 2 studies, 6,684 participants; I2=0%), depression (difference= 0.12, 95% CI -0.04 to 0.28; 1 study, 217 participants), general mental health (difference= -0.03, 95% CI -0.09 to 0.04; 3 studies, 18,985 participants; I2=94%), stress (difference= 0.04, 95% CI -0.11 to 0.18; 1 study, 217 participants).InterpretationMental health outcomes did not differ or were somewhat worse among women than men.