Trajectories of psychological distress and associated factors: A Yokohama longitudinal survey

Abstract Introduction Mental health promotion has become a global priority, as high psychological distress is a key indicator of impaired mental health and well-being. Urban areas such as Yokohama, Japan, face complex social and mental health challenges-including demographic shifts and high living costs-that add urgency to this issue. In response, national and local governments have increased efforts to support residents from both economic and health perspectives. However, there is limited evidence on the actual experiences of residents. Understanding the recent trends and characteristics of individuals experiencing psychological distress, as well as exploring explanatory factors, is crucial for guiding future interventions targeting at-risk populations. This study addresses two research questions: 1. What are the patterns of psychological distress in Yokohama? and 2. Which factors explain these patterns? Using a longitudinal data, we describe trajectory groups of psychological distress and explore factors that may influence changes in distress. Methods We used data from HAMA study, a longitudinal survey of Yokohama residents aged 20-59, based on participation requests sent to 10,000 randomly selected households. This ongoing survey has been conducted annually since 2023. For the present analysis, we applied group-based trajectory modeling to identify clusters of individuals with similar patterns of psychological distress, as measured by Kessler Psychological Distress Scale (K6), across three waves from 2023 to 2025. After describing the characteristics of each group, we selected potential explanatory factors to further investigate their relationships with psychological distress over time. Results We analyzed participants who completed all three survey waves excluding those who provide no response to any K6 items. Preliminary analysis revealed six distress patterns. Descriptive analysis indicates variation in patterns based on socioeconomic, health, and occupational factors. Key messages • We used a longitudinal survey between 2023-2025, and identified six psychological distress patterns across three waves. • Preliminary findings suggest that occupational conditions, especially work–life balance, may be crucial in explaining observed patterns, alongside socioeconomic and health factors.