Is change in mental distress among adolescents predicted by sedentary behaviour or screen time? Results from the longitudinal population study The Tromsø Study: Fit Futures

OBJECTIVE: There is growing interest in the relationship between sedentary behaviour and mental distress among adolescents, but the majority of studies to date have relied on self-reported measures with poor validity. Consequently, current knowledge may be affected by various biases. The aim of this study was to investigate the cross-sectional and longitudinal association between (1) objectively measured sedentary time and (2) self-reported screen time with mental distress among adolescents participating in The Tromsø Study: Fit Futures, in order to see if the association is dependent on mode of measurement of sedentary behaviour. DESIGN: Prospective study. SETTING: Sample drawn from upper secondary school students (mean age 16.3 years at baseline) from two municipalities in Northern Norway participating in The Tromsø Study: Fit Futures 1 and 2. PARTICIPANTS: 686 adolescents (54.5% female), with complete self-reported and accelerometer data after multiple imputation. PRIMARY OUTCOME MEASURES: Mental distress assessed via the Hopkins Symptom Checklist-10 (HSCL-10). RESULTS: Minutes in sedentary behaviour measured by accelerometer showed no significant relationship with mental distress in neither crude, partly adjusted nor multiple adjusted hierarchic linear regression analyses. Self-reported screen time was positively associated with mental distress in all analyses (multiple adjusted, B=0.038, p=0.008, 95% CI 0.010 to 0.066). However, the effect was small. CONCLUSIONS: Self-reported screen time was associated with slightly elevated mental distress 2 years later, whereas objectively measured minutes in sedentary behaviour was not, indicating a discrepancy in the results depending on measurement methods.