In Reply We appreciate the opportunity to engage in scholarly discussion surrounding our contribution to JAMA Pediatrics on the association of screen time and depression in adolescence.1 Teh et al state that our cohort is unlikely to be representative of the entire adolescent population because adolescents within this cohort were originally selected for another study evaluating the efficacy of a prevention program targeting adolescent substance through personality. The authors did not appreciate the epidemiologic nature of the CoVenture Sample, which included approximately 85% of all children attending the seventh grade in 31 high schools across the greater Montreal, Quebec, Canada, area. These schools were selected from each of the school districts in the greater Montreal area, included 15% of all schools, and were shown to be representative of their respective school districts on socio-demographic indicators. The CoVenture cohort did not specify any eligibility or exclusion criteria, with the exception that students had to volunteer and assent to the research. Intervention was offered to a subgroup of youth, and this was included as a covariate and moderator in the analyses and was not shown to affect the reported findings. Teh et al also discuss potential confounding variables. We did not have measurements on the confounders they mentioned, prohibiting the modeling of effects for these factors over time. We encourage other researchers to consider time-varying mediators and moderators of the screen time-depression association. Furthermore, Teh et al question the validity of the Brief Symptoms Inventory,2 which we used to measure depressive symptoms. However, previous work2 has demonstrated that the Brief Symptoms Inventory has high test-retest reliability and good construct and convergent validity. Nevertheless, we encourage other researchers to study the association of screen time and depression using the measuring tools proposed by Teh et al. Most notably, Teh et al argue that it is not possible to conclude definitively that greater social media and television use are associated with more severe symptoms of depression. Specifically, Teh et al highlight that adolescents’ mental well-being determines their social media use. They argue that adolescents with preexisting depressive symptoms are more likely to use social media and have a greater tendency to use it in a negative way. Although we cannot draw causal conclusions, we modeled the association of year-to-year changes in screen time with depression, while also accounting for common vulnerability between variables and natural within-person developmental trends across behaviors. Therefore, including the between-person effects in the model when investigating within-person effects accounts for any potential confounding of baseline depression. The significant within-person effects are strong indicators that increases in adolescents’ social media and television use within a given year are associated with more severe symptoms of depression within that same year. Moreover, we agree with the Teh et al argument that those with preexisting depressive symptoms are more inclined to use social media in a negative way. We tested this assumption based on the reinforcing spirals hypothesis,3 which was confirmed by showing convergent effect across between-person effects and within-person effects and a positive interaction between these effects regarding the association of social media use and depression among adolescents. This effect was interpreted as being additive beyond the robust within-person effects: as social media increases, so does depression, but in the context of high levels of depression, increases in social media are associated with more robust increases in depression.
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Boers E, Afzali MH, Conrod P. Association of Media Screen Time Use With Depression in Adolescents—Reply. JAMA Pediatr. 2020;174(2):210. doi:10.1001/jamapediatrics.2019.4920
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