The Effects of Higher Education on Midlife Depression: Quasi-Experimental Evidence from South Korea

Higher education has expanded worldwide, with women outpacing men in many regions. While educational attainment is consistently linked to better physical health, its mental health effects - particularly for women - remain underexplored, and causal evidence is limited. We estimate the impact of college completion on depression among middle-aged women in South Korea, leveraging the 1993 higher education reform, which raised women’s college attainment by 45 percentage points (pp) over the following decade. We use two nationally representative datasets to triangulate evidence, including the Korea National Health and Nutrition Examination Survey (KNHANES, 2007-2021) for physician-diagnosed depression, and the Korean Longitudinal Survey of Women and Families (KLoWF, 2007-2022) to validate findings using self-reports of depressive symptoms. We implement two-stage least squares (2SLS) with a birth-cohort instrument based on exposure to the reform (within 3 years of the cutoff in KNHANES and within 1 to 3 years in KLoWF). In KNHANES, college completion lowers physician-diagnosed depression by 2.4 pp, attenuating to 1.6 pp after adjusting for income, employment, and physical health. In KLoWF, college completion improves self-reported mental health. The weekly depressive-symptoms composite declines by 17.4 pp, attenuating to 16.4 pp after covariate adjustment. Placebo tests on unaffected cohorts yield null results. This study contributes to the growing quasi-experimental literature on education and mental health with convergent evidence across clinical diagnoses and self-reported depressive symptoms in South Korea. By focusing on college education in a non-Western setting, it extends the external validity of existing findings and highlights educational policy as a potential lever to reduce the burden of midlife depression among women.

💡 Research Summary

This paper exploits the 1993 higher‑education reform in South Korea as a natural experiment to identify the causal impact of college completion on mid‑life depression among women. The reform dramatically relaxed admission quotas and expanded university capacity, raising women’s college enrollment by roughly 45 percentage points for cohorts born around the policy cutoff. Using two nationally representative data sources— the Korea National Health and Nutrition Examination Survey (KNHANES, 2007‑2021) for physician‑diagnosed depression and the Korean Longitudinal Survey of Women and Families (KLoWF, 2007‑2022) for self‑reported depressive symptoms— the authors implement a two‑stage least squares (2SLS) design. The instrument is a birth‑cohort indicator: women born within three years of the 1974 cutoff (KNHANES) or within one to three years (KLoWF) are considered “exposed” to the reform, while adjacent cohorts serve as the control group.

In the first stage, exposure to the reform raises college completion rates by about 45 pp, with an F‑statistic well above conventional thresholds, confirming instrument relevance. The second stage estimates the effect of college completion on depression. In KNHANES, college graduation reduces the probability of ever having been diagnosed with depression by 2.4 percentage points; after adjusting for income, employment, and physical health, the effect attenuates to 1.6 pp but remains statistically significant. In KLoWF, the weekly depressive‑symptom composite falls by 17.4 pp (≈16 pp after covariate adjustment). Narrower cohort windows (±1 year) produce similar magnitudes, while broader windows (±2 or ±3 years) yield even larger point estimates, suggesting robustness to bandwidth choice.

The authors explore mediation by estimating the same 2SLS framework with economic conditions (household income, full‑time employment) and physical health (chronic disease, BMI) as intermediate outcomes. Income and stable employment each account for roughly 9 pp and 1 pp of the depression reduction, respectively, while health behaviors (smoking, drinking, preventive check‑ups) contribute minimally (<1 pp). This pattern supports a “flexible resources” mechanism: higher education improves material and health resources, which in turn lower depression risk.

Extensive robustness checks bolster credibility: (1) placebo regressions on cohorts unaffected by the reform show null effects; (2) inclusion of year and region fixed effects does not alter the main coefficients; (3) sensitivity analyses varying the cohort bandwidth (3, 5, 10, 15 years) preserve the sign and significance of the estimates; (4) tests for pre‑trend differences between exposed and control cohorts reveal no systematic divergence before the policy change.

Limitations are acknowledged. The sample is restricted to women aged 40‑65, limiting generalizability to men or other age groups. Unobserved shocks coinciding with the reform (e.g., labor‑market reforms, cultural shifts) could bias the exclusion restriction, although the placebo tests mitigate this concern. Finally, the lack of data on adolescent mental health prevents a full test of reverse causality (early‑life depression influencing educational attainment).

The study contributes to the sparse quasi‑experimental literature on education and mental health, especially outside Western contexts. By triangulating clinical diagnoses with self‑reported symptom scales, it demonstrates consistent protective effects of college education on depression. Policy implications are clear: expanding access to higher education, particularly for women, can generate substantial mental‑health benefits beyond the well‑documented economic returns, offering a cost‑effective lever for reducing the burden of mid‑life depression in South Korea.