Abstract
While some types of rumination have been reported as exacerbating factors in depressive symptoms related to attention-deficit/hyperactivity disorder (ADHD) traits, the role of self-rumination remains underexplored. Additionally, self-reflection-a similar form of private self-consciousness which may have protective effects-has been even less examined. This study of 3,000 Japanese adults (aged 18-50 years) investigates self-rumination and self-reflection in depressive symptoms related to ADHD, using the Adult ADHD Self-Report Scale, Rumination-Reflection Questionnaire, and Beck Depression Inventory-II. Statistical analyses included Pearson's correlation and linear regression for mediation/moderation. ADHD traits were correlated with depressive symptoms (r = 0.413, p < 0.001), mediated by self-rumination (indirect effect = 0.21, 95% confidence interval [0.17, 0.26]). Self-reflection was positively correlated with depressive symptoms (r = 0.193, p < 0.001) but had a protective effect when controlling for self-rumination (β = -0.75, p < 0.001). Moderated mediation analysis showed self-reflection reduced depressive symptoms related to ADHD traits by moderating both the impact of ADHD traits on self-rumination and the influence of self-rumination on depressive symptoms. These effects were particularly significant for inattention traits. Our findings suggest that self-reflection, by mitigating self-rumination, may serve as a therapeutic target for depressive symptoms in adults with ADHD traits.