When does depression become a disorder? Using recurrence rates to evaluate the validity of proposed changes in major depression diagnostic thresholds.

High community prevalence estimates of DSM-defined major depressive disorder (MDD) have led to proposals to raise MDD's diagnostic threshold to more validly distinguish pathology from normal-range distress. However, such proposals lack empirical validation. We used MDD recurrence rates in the longitudinal 2-wave Epidemiologic Catchment Area Study to test the predictive validity of three proposals to narrow MDD diagnosis: a) excluding "uncomplicated" episodes (i.e., episodes that last no longer than 2 months and do not include suicidal ideation, psychotic ideation, psychomotor retardation, or feelings of worthlessness); b) excluding mild episodes (i.e., episodes with only five to six symptoms); and c) excluding nonmelancholic episodes. For each proposal, we used lifetime MDD diagnoses at wave 1 to distinguish the group proposed for exclusion, other MDD, and those with no MDD history. We then compared these groups' 1-year MDD rates at wave 2. A proposal was considered strongly supported if at wave 2 the excluded group's MDD rate was not only significantly lower than the rate for other MDD but also not significantly greater than the no-MDD-history group. Results indicated that all three excluded groups had significantly lower recurrence rates than other MDD (uncomplicated vs. complicated, 3.4% vs. 14.6%; mild vs. severe, 9.6% vs. 20.7%; nonmelancholic vs. melancholic, 10.6% vs. 19.2%, respectively). However, only uncomplicated MDD's recurrence rate was also not significantly greater than the MDD occurrence rate for the no-MDD-history group (3.4% vs. 1.7%, respectively). This low recurrence rate resulted from an interaction between uncomplicated duration and symptom criteria. Multiple-episode uncomplicated MDD did not entail significantly elevated recurrence over single-episode cases (3.7% vs. 3.0%, respectively). Uncomplicated MDD's general-distress symptoms, transient duration, and lack of elevated recurrence suggest it may generally represent nonpathologic intense sadness that should be addressed in treatment guidelines and considered for exclusion from MDD diagnosis to increase the validity of the MDD/normal sadness boundary.