BACKGROUND: Depression and anxiety symptoms among adolescents have increased in recent years, making the identification of modifiable risk factors important. Prolonged screen time (ST) and later chronotype may be independently and jointly associated with adolescent mental health. This study aimed to examine the independent and joint associations of ST and chronotype with depression and anxiety symptoms among adolescents.
METHODS: Data were drawn from the China Adolescent Health Screening Program (CAHSP), a large school-based health screening program conducted in Shenzhen, southern China, using a multistage cluster sampling design, including 10,083 adolescents (mean age: 13.7 [SD: 1. 6] years). ST was assessed using structured self-report items, while chronotype was measured using the Morningness-Eveningness Questionnaire-5 (MEQ-5). Depression and anxiety symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder-7 (GAD-7), respectively. Logistic regression models adjusted for relevant covariates were employed to examine independent and joint associations of ST and chronotype with depression and anxiety symptoms.
RESULTS: Excessive ST and later chronotype were significantly associated with depression and anxiety symptoms. Significant interaction indicated that the association between excessive ST and mental health symptoms differed across chronotype groups. Stratified analyses confirmed that within each chronotype group, adolescents with excessive ST had higher odds of depression and anxiety, with the strongest associations observed in evening chronotype (E-type) adolescents (depression: aOR = 2.54, 95% CI: 2.01-3.22; anxiety: aOR = 2.49, 95% CI: 1.98-3.13). Joint analyses further confirmed that E-type adolescents with excessive ST showed the highest odds of screening positive for depression and anxiety symptoms (depression: aOR = 5.55, 95% CI: 4.38-7.02; anxiety: aOR = 4.71, 95% CI: 3.73-5.93) compared with the non-excessive ST and M-type group.
CONCLUSION: Higher levels of ST and later chronotype were associated with higher odds of screening positive for depression and anxiety symptoms among adolescents. Public health strategies to promote adolescents' mental well-being should focus on encouraging healthy screen behaviors and promoting sleep hygiene, particularly for E-type adolescents.
