Abstract:   Co-rumination refers to excessively discussing personal problems within a dyadic relationship. The meta-analysis examined how co-rumination was correlated with gender, mental health, and relationship quality. Our results revealed (1) Female co-ruminate more than male (g = 0.57, p < 0.001), which appeared most significantly in adolescents, especially for friends; (2) co-rumination was significantly correlated with mental health (r = 0.15, p < 0.001); and this effect is still significantafter controlling the rumination (partial correlation r = 0.08, p < 0.001); (3) age, study design, and co-ruminator didn’t moderate the aggregated correlation; (4) The aggregated correlation between co-rumination and relationship quality was also significant (r = 0.42, p < 0.001). Future research should further examine the causal relationship between co-rumination and mental health.

Key words: meta-analysis, co-rumination, gender difference, internalizing problems, relationship quality