The impact of learning modalities and sleep quality on adolescent mental health: a cross-sectional study.

Background: Adolescents' mental health and sleep have been significantly affected during the COVID-19 pandemic, yet differences between home-based online learning and in-school learning remain unclear. Methods: A cross-sectional survey was conducted among 5,787 students in Grades 7-12 from 14 schools in Gansu Province, China, in 2020 and 2021. Mental health and sleep were assessed using standardized questionnaires. Statistical analyses included reference comparisons with normative data, two-way analysis of variance with effect sizes, multinomial logistic regression for PHQ-9 depressive symptom severity, and multiple linear regression using the enter method for MMHI-60 total average scores. Results: Students showed higher psychological distress compared with national norms across multiple domains. In-school learning was associated with significantly higher psychological distress and depressive symptoms compared to home-based online learning ( Conclusion: Learning modality (in-school vs. home-based) and sleep quality are independently associated with adolescent mental health. Students in in-school settings report higher psychological distress than those learning at home. Interventions promoting sleep hygiene and creating supportive school environments may be beneficial, though causal effects cannot be established due to the cross-sectional design.