Age-varying associations between lifestyle risk factors and major depressive disorder: a nationally representative cross-sectional study of adolescents

Purpose: Lifestyle risk factors, such as alcohol use, smoking, high body mass index, poor sleep, and sedentary behavior, represent major public health issues for adolescents. These factors have been associated with increased rates of major depressive disorder (MDD). The purpose of this paper is to investigate critical peaks in the prevalence of MDD at certain ages and to examine how these peaks might be amplified or attenuated by the presence of lifestyle risk factors. Methods: A nationally representative sample of adolescents aged 11–17\ua0years old (n = 2967) and time-varying effect models were used to investigate the associations between lifestyle risk factors and the prevalence of MDD by sex. Results: The estimated prevalence of MDD significantly increased among adolescents from 4% (95% CI 3–6%) at 13\ua0years of age to 19% (95% CI 15–24%) at 16\ua0years of age. From the age of 13, males were significantly less likely to have a diagnosis of MDD than females with the maximum sex difference occurring at the age of 15 (OR 0.24, 95% CI 0.13–0.47). All lifestyle risk factors were at some point significantly associated with MDD, but these associations did not differ by sex, except for body mass index. Discussion: These findings suggest that interventions designed to prevent the development of depression should be implemented in early adolescence, ideally before or at the age of 13 and particularly among young females given that the prevalence of MDD begins to rise and diverge from young males. Interventions should also simultaneously address lifestyle risk factors and symptoms of major depression