Meta-analysis: To "know thyself" can hurt your mental health. Self-reflection, centered on the introspection and evaluation of one’s thoughts, feelings, and behaviors in relation to self-concerns, occupies a central place in understanding the dynamics of mental health. Nonetheless, the relationship between self-reflection and mental health is a source of continuous controversy. This study represents the first meta-analysis to systematically investigate the relationship between self-reflection and mental health within the dual-factor model framework. We found that self-reflection was significantly associated with negative mental health but not with positive mental health. The random-effect model showed no significant relationship between self-reflection and overall positive mental health or with individual positive indicators, including subjective well-being, life satisfaction, and self-esteem. In contrast, the model showed a significant positive relationship between self-reflection and overall negative mental health indicators, including depression and anxiety. This finding aligns with earlier studies  and underscores that high levels of self-reflection are often linked with various mental health challenges Furthermore, in clinical treatment, when individuals enhance their self-reflection abilities, they often become aware of previously unnoticed emotions, such as sadness. This can lead to depressive mood and distress. [Some] observations suggest that while moderate self-reflection supports normal social and emotional functioning, significant deviations in self-reflection may be associated with various psychopathology.