Mental Health

Phase-Specific Changes in Korean Adolescents' Health Behaviors and Mental Health Across COVID-19 School Closure and Reopening.

Park E • The Journal of school health • 2026

TL;DR

Recovery was uneven across health domains among Korean adolescents, identifying school reopening as a critical prevention window requiring sustained, phase-specific intervention.

Key Findings

Results

Current smoking among Korean adolescents declined from the pre-pandemic phase to the post-pandemic phase.

Prevalence fell from 6.4% (95% CI, 6.1-6.7) pre-pandemic to 3.8% (3.6-4.0) post-pandemic.
Data came from the nationally representative Korea Youth Risk Behavior Survey (2018-2024).
Weighted prevalence estimates were compared across four phases: pre-pandemic, pandemic, transition, and post-pandemic.

Results

Breakfast skipping increased from the pre-pandemic phase to the post-pandemic phase.

Prevalence rose from 34.5% (34.0-34.9) pre-pandemic to 41.6% (41.1-42.0) post-pandemic.
The analytic sample included 376,066 adolescents (51.8% boys).

Results

Moderate-to-vigorous physical activity exceeded its pre-pandemic level in the post-pandemic phase.

This was reported as a post-pandemic recovery in physical activity.
Despite this, obesity prevalence rose over the same period.

Results

Obesity prevalence increased from the pre-pandemic to the post-pandemic phase.

Prevalence rose from 10.9% (10.7-11.2) pre-pandemic to 12.2% (11.9-12.5) post-pandemic.
The increase occurred even though moderate-to-vigorous physical activity exceeded its pre-pandemic level.

Results

Suicidal ideation decreased during the pandemic phase but peaked during the transition (school reopening) phase.

Suicidal ideation reached 14.0% (13.6-14.5) during the transition phase.
The pattern suggests mental health risk was highest during school reopening rather than during closure.

Conclusions

Recovery of adolescent health was uneven across health domains, and school reopening is identified as a critical prevention window.

Substance use improved, whereas diet quality (breakfast skipping), obesity, and transition-phase suicidal ideation worsened.
The author recommends strengthening healthy meal and physical activity programs, sustaining substance-use prevention, and ensuring equitable access to mental health screening and referral during reopening.

What This Means

This study used a large national survey of Korean middle and high school students from 2018 to 2024 (about 376,000 adolescents) to see how health behaviors and mental health changed before, during, and after COVID-19 school closures, including the period when schools reopened. It compared four phases: pre-pandemic, pandemic, transition (reopening), and post-pandemic. The changes were mixed. Smoking dropped from 6.4% to 3.8%, and physical activity returned to above pre-pandemic levels. However, skipping breakfast became more common (34.5% to 41.6%) and obesity rose (10.9% to 12.2%) even though activity had recovered. Suicidal thoughts fell during the pandemic but peaked at 14.0% during the reopening transition. This research suggests that the return to school is a vulnerable period when different health areas can move in different directions. The author argues that schools could use reopening as a window to strengthen meal and physical activity programs, keep up substance-use prevention, and make mental health screening and referral available to all students. As an observational survey comparison across time periods, it describes changes but does not prove what caused them.

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Citation

Park E. (2026). Phase-Specific Changes in Korean Adolescents' Health Behaviors and Mental Health Across COVID-19 School Closure and Reopening.. The Journal of school health. https://doi.org/10.1111/josh.70267

Key Findings

What This Means

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