Early-life residential mobility as a social determinant of mood disorder risk: A nationwide longitudinal cohort study in South Korea.

BACKGROUND: Residential mobility during childhood has been widely discussed as a potential source of psychosocial disruption, yet population-level longitudinal evidence remains limited outside Western contexts. This study examined whether early-life residential mobility is associated with the subsequent risk of mood disorders in South Korea. METHODS: We conducted a nationwide retrospective cohort study using the Korean National Health Insurance Service database (N = 6,668,197). Residential mobility was assessed over a six-year period spanning late childhood and early adolescence (ages 10 to 15). Incident clinical diagnoses of mood disorders (ICD-10: F31 to F39) were ascertained between ages 16 and 25. Multivariable Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals, adjusting for key available covariates, including sex and household income. RESULTS: A greater frequency of residential relocation was significantly associated with a higher risk of mood disorders. Relative to non-movers, the adjusted hazard ratios were 1.12 (95% CI: 1.12-1.13) for 1-move, 1.27 (95% CI: 1.25-1.28) for 2-move, and 1.41 (95% CI: 1.38-1.44) for 3+ moves. Associations were stronger among lower-income groups, and similar graded patterns were observed across diagnostic subtypes. Sensitivity analyses excluding early diagnoses yielded comparable results. Early-life residential mobility was associated with an elevated and progressively increasing risk of mood disorders in South Korea. CONCLUSIONS: These findings underscore the importance of residential stability during sensitive developmental periods and suggest that residential mobility may represent a potentially modifiable social and environmental risk factor for later mental health. Future research incorporating intergenerational data may help clarify underlying mechanisms.