How prevalent and morbid are subthreshold manifestations of major depression in adolescents? A literature review

Introduction: Major Depressive Disorder (MDD) among youth is a public health concern. Our aim was to examine the current body of knowledge to better characterize the prevalence and morbidity associated with subthreshold forms of MDD among youth. Given that MDD tends to develop gradually over time, we hypothesized a high prevalence and considerable impairment associated with youth suffering from depressive symptoms that fall short of full, syndromic status. Methods: A literature search was conducted using PubMed exclusively to identify studies assessing the prevalence and clinical characteristics of subthreshold MDD in adolescents. Results: Six scientific papers that met our priori inclusion and exclusion criteria were identified. All papers sampled adolescents. The prevalence of subthreshold MDD ranged from 5% over the past year, to 29% over the two weeks prior to screening. These papers reported clinically significant morbidity associated with subthreshold MDD among adolescents, with evidence for elevated rates of psychiatric comorbidities, impaired functioning in social and familial domains, increased suicidality, and frequent mental health service utilization. Limitations: Though we examined a sizeable and diverse sample, we only identified six cross-sectional informative studies for this review. Variability of subthreshold MDD and major outcome definitions across studies, likely limits the specificity of findings. Conclusions: Subthreshold MDD is prevalent among youth, and is associated with emotional and social impairments that reach the level of obtaining clinical care. These findings could lead to early intervention efforts aimed at mitigating the adverse outcomes associated with subthreshold MDD as well as the progression to full syndrome MDD. Our review documents that regardless of whether progression to full diagnostic status occurs, this condition is morbid.