Remission is insufficient: predictors and mechanistic models of recurrence in late-life depression

While achieving remission is the goal of acute antidepressant treatment, recurrence of new depressive episodes following remission is unfortunately common in clinical populations with Major Depressive Disorder, including older adults with Late-Life Depression (LLD). The neurobiological factors underlying this risk are poorly understood, limiting our ability to identify potential preventive mechanistic targets. Beyond the limited prognostic utility achieved from individual psychiatric history, it remains challenging to clinically stratify individual risk. This review examines factors influencing the recurrence of depressive episodes following remission in LLD, focusing on cognitive, behavioral, social, and environmental aspects. It additionally considers neuroimaging-based biomarkers related to recurrence risk as well as discussing evidence for and limits of maintenance treatment to prevent recurrence. The paper proposes possible mechanisms contributing to recurrence, including physiological and behavioral responses to stressors, the influence of Alzheimer's disease neuropathology, and conceptualizing repeat depressive episodes within the accelerated aging hypothesis of LLD. A dynamical landscape model of depression recurrence is proposed to elucidate the interplay between different mood states, resilience, and treatment response. This synthesis then highlights avenues for future research, focusing on areas of potential significance ranging from risk stratification to tertiary prevention efforts that may improve both long-term affective and cognitive symptoms.