Divergent trajectories of psychological distress during the prolonged COVID-19 pandemic in Japan.

Psychological responses to the COVID-19 pandemic showed heterogeneous trajectories rather than uniform recovery. We analyzed seven waves of nationwide web-based surveys conducted in Japan between June 2020 and December 2022 (approximately 1,000 participants per wave) to examine long-term trends in depression, anxiety, and stress and their associations with self-evaluative traits. DASS-21 scores were significantly elevated during the initial emergency phase (June 2020) and declined substantially thereafter (Kruskal-Wallis tests, all p < .001). However, distributional analyses indicated that a subgroup of individuals remained persistently distressed despite overall population-level improvement. Decision-tree-based variable-importance analyses identified the impostor phenomenon as the strongest contributor to depression, anxiety, and stress, followed by self-esteem. For anxiety, survey timing showed the strongest linear association, whereas non-linear models consistently highlighted self-evaluative variables as dominant predictors. These findings indicate that prolonged societal crises are associated with divergent mental-health adaptation patterns. Psychological self-evaluation factors, particularly impostor feelings and low self-esteem, may play a central role in persistent distress beyond demographic and social-network factors.