Contributing factors to heterogeneity in the timing of the onset of major depressive episode: Results from a national study.

It remains unclear whether specific clinical factors contribute to heterogeneity in the timing of the onset of major depression. Using a nationally representative US adult sample, the second wave of the National Epidemiologic Survey on Alcohol and Related Conditions, we compared the characteristics of 5 different groups of patients defined by their age at onset: (i) before 18 years, (ii) between 18 and 34 years, (iii) between 35 and 44 years, (iv) between 45 and 59 years, and (v) 60 years or older. Specifically, we examined parental history of psychiatric disorders, history of childhood maltreatment experiences, sociodemographic characteristics, lifetime psychiatric disorders, and psychiatric disorders that occurred before the first major depressive episode (MDE). Compared with first MDE occurring between 18 and 34 years, first MDE before 18 years was more strongly associated with childhood maltreatment and family history of psychiatric disorders, and less strongly linked to prior lifetime psychiatric disorders, whereas first MDE occurring at 60 years and older was more strongly associated with widowhood and a prior lifetime history of generalized anxiety disorder. Associations found cannot be interpzreted as causal relationships due to study design and the risk of recall bias. Our results suggest substantial age differences in risk factors for first MDE. Improving early detection and treatment of major depression and other psychiatric disorders, and preventing childhood maltreatment may have broad benefits to reduce the burden of MDE at all ages