Heterogeneity in the longitudinal course of depressive symptomatology in adults with a history of recurrent major depressive disorder

BACKGROUND: Depression is highly heterogeneous. Characteristics of previous depressive episodes, additional clinical difficulties, family history of depression and exposure to stressors are associated with poorer outcomes. However, the role of these factors has not been tested simultaneously to explain depression persistence. METHODS: Using longitudinal data from 337 adults with a history of recurrent MDD, we characterised depressive symptom trajectories over 13-years using growth mixture modelling. We tested two partially competing hypotheses as to why depression persists: a) persistent depression is aetiologically distinct from a less persistent course and/or b) persistent depression is largely explained by exposure to ongoing stressors. RESULTS: Three trajectory classes were identified: low (64%), which showed minimal symptoms throughout the study period; intermediate (17%), which showed high baseline symptoms which lessened after the first assessment; and severe persistent (19%), which showed high depressive symptoms throughout the study period. Three variables differentiated the severe persistent class: history of a severely impairing episode, self-harm or suicide attempt at baseline and ongoing high perceived stress. LIMITATIONS: The sample consisted of primarily women therefore the results may not generalise to men. An 8-year period between the third and fourth assessment meant that estimates of depression may have been conservative. CONCLUSIONS: Prior impairment, self-harm or suicide and perceptions of stress were associated with a persistent course. It may be helpful for practitioners to consider assessing these factors to identify adults at the greatest risk of developing persistent depression.