Teacher-led MHL Education in Japanese Preteens

This study used a cluster randomized controlled trial design, with randomization at the school level. Eight public elementary schools in Kanazawa City were assigned to either intervention or control groups using simple randomization by external staff not involved in implementation.

The intervention, the Short Mental Health Literacy Program (SMHLP), consisted of a 45-minute classroom lesson delivered by homeroom teachers. The lesson included three parts: a slide-based introduction to mental health, a 10-minute original animation about a student experiencing psychological stress, and a worksheet-based reflection activity. Teachers used self-guided materials including videos and manuals to prepare.

Primary outcome measures included an 8-item true/false knowledge scale (range: 0-8), a 5-item social distance scale (range: 5-20), and binary-response questions on help-seeking intention and willingness to support peers. The internal consistency of the knowledge scale was acceptable (Cronbach's α = 0.65), and that of the stigma scale was good (Cronbach's α = 0.88).

Data were collected at three time points: before the intervention (T1), immediately after (T2), and three months later (T3). **Statistical analyses were conducted using linear mixed models (LMM) for continuous outcomes and logistic regression mixed models (LRMM) for binary outcomes. Three-level hierarchical structures were modeled for LMM, with time nested within students and students nested within schools. School-level clustering was adopted. For LRMMs, two-level models were used without random effects for schools due to convergence issues. Intention-to-treat analyses were conducted.** Subgroup analyses were performed by grade level.

Parental opt-out consent procedures were used, and verbal assent was obtained from students. The study was approved by the University of Tokyo Human Research Ethics Committee (Approval No. 15-118).

Inclusion criteria

• Students enrolled in 5th or 6th grade at one of the eight participating public elementary schools in Kanazawa, Japan.
• Aged 10-12 years old.
• Passive consent obtained from guardians; verbal assent obtained from children.
• Able to complete self-report questionnaires.

Exclusion criteria

• Students whose parents/guardians opted out of the study.

Note: Students who were absent on the day of the pre-test (T1) were excluded from the analysis population but not from the initial study cohort.