Rest-Activity Rhythms as Digital Biomarkers: Predicting Relapse in Major Depressive Disorder via Actigraphy

The Challenge of Relapse in Major Depressive Disorder

Major depressive disorder (MDD) is a chronic and recurrent condition that imposes a staggering burden on global health systems. Despite the availability of various pharmacotherapeutic and psychotherapeutic interventions, a significant proportion of patients experience a relapsing-remitting course. Predicting these relapses remains one of the most formidable challenges in clinical psychiatry. Historically, clinicians have relied on subjective patient self-reports or intermittent clinical interviews—methods that are often hindered by recall bias and the late appearance of symptoms.

There is an urgent clinical need for objective, continuous, and non-invasive biomarkers that can signal an impending depressive episode before a full clinical relapse occurs. Recent advances in wearable technology, specifically actigraphy, have opened new avenues for digital phenotyping. By monitoring rest-activity rhythms (RARs) and sleep-wake cycles in a naturalistic environment, actigraphy provides a high-resolution window into the biological rhythms that are frequently disrupted in mood disorders.