Psychological distress among Japanese high school students during the COVID-19 pandemic: An energy landscape analysis.

Before the COVID-19 pandemic, the healthy psychological state occurred 11.0 times as frequently as the depressive state among high school students.

• Analysis was based on monthly K6 questionnaire responses from 84 participants aged 16-18 years (42 males, 42 females) in the pn-TTC cohort in Tokyo, Japan.
• 1,278 total responses were collected from July 2019 to September 2021.
• The healthy state was defined as a configuration in which all six K6 items are below each participant's individual mean; the depressive state was defined as all six K6 items above the individual mean.
• The pre-pandemic baseline ratio of healthy to depressive state frequency was 11.0.

During the COVID-19 pandemic, the relative frequency of the healthy state increased compared to the pre-pandemic period.

• During the pandemic, the relative frequency of the healthy state was 18.2, 18.5, and 15.0 times that of the depressive state across successive pandemic time periods.
• This represents an increase from the pre-pandemic ratio of 11.0.
• The evolving energy landscape revealed an association between the pandemic period and a lower likelihood of being in a depressive state.
• These findings were contrary to some prior reports suggesting increases in psychological distress during COVID-19.

Two distinct groups of students with different K6 dynamics and energy landscapes were identified.

• Group 1 consisted of 61 participants whose total K6 score was relatively low (less than 5) and stable over time.
• Group 2 consisted of 23 participants whose total K6 score was higher (with most being higher than 5) and less stable.
• The two groups differed in both their K6 dynamics and their corresponding energy landscapes.

The group with higher and less stable K6 scores showed greater changes in cortical thickness in the caudal middle frontal gyrus (cMFG) in the direction of accelerated adolescent brain development.

• The difference in cortical thickness change in the cMFG was statistically significant (t-statistic = -2.36, p-value = 0.019, q-value = 0.048).
• Cortical thickness was measured by magnetic resonance imaging.
• The change was described as being in the direction of accelerated adolescent brain development.

The group with higher and less stable K6 scores also showed greater changes in cortical thickness in the temporal pole (TP) in the direction of accelerated adolescent brain development.

• The difference in cortical thickness change in the temporal pole was statistically significant (t = 3.08, p = 0.0023, q = 0.012).
• Cortical thickness was measured by magnetic resonance imaging.
• The association between psychological states and brain development was described as descriptive, and the authors noted that future studies are needed to examine causality.

Energy landscape analysis, derived from statistical physics, was applied to model multivariate psychological states as a dynamic system of interactions among K6 questionnaire items.

• The method models interactions among all six K6 items rather than summarizing them into a single composite score.
• It was used to visualize longitudinal changes in psychological distress before and during the COVID-19 pandemic.
• The authors argue this approach may improve mental health surveillance for future pandemics.
• The study compared this method against conventional statistical approaches that use composite scores.

The study was conducted in a population-based longitudinal cohort (pn-TTC) in Tokyo, Japan, with generalizability limited to that population.

• All 84 participants lived in Tokyo, Japan.
• The pn-TTC is described as a population-based longitudinal study that follows children to investigate developmental and mental health trajectories.
• Participants were 16- to 18-year-old high school students.
• The authors noted that generalizability remains limited due to the single-city sample.