Feeling Supported, Perceived Usefulness, and Psychological Distress Among Adults in Japan: A Cross-Sectional Study

Background/Objectives: Feeling supported and perceiving oneself as useful to others may be associated with psychological distress. We examined these associations and exploratory nonlinear and interaction patterns in a general-population internet sample in Japan. Methods: This cross-sectional secondary analysis included 10,199 respondents aged ≥20 years from the Survey on Satisfaction and Quality of Life, 2025. The two social perceptions were single items scored 0-10. A six-item K6-derived distress score (0-24) used a modified reference period. Covariate-adjusted ordinary least squares regression included centered linear, quadratic, and product terms, with HC3 robust inference. Results: Near the centering values, feeling supported (B = -0.552, 95% CI -0.620 to -0.484) and perceived usefulness (B = -0.744, 95% CI -0.816 to -0.673) were inversely associated with distress. Both quadratic terms were positive in the primary model. The negative interaction (B = -0.050, 95% CI -0.081 to -0.019) added only 0.0011 to R². Its magnitude varied with range restriction and additional covariates; log-transformed and spline analyses also indicated a joint association. The age group modification estimate was imprecise (B = 0.059, 95% CI -0.023 to 0.140). Conclusions: Both perceptions were associated with lower distress. The exploratory interaction explained little additional variance and does not establish a mechanism, clinical benefit, or absence of age differences.