tDCS: Sleep to Mood in Depression (S2M-D)

This study evaluates the effects of home-based transcranial direct current stimulation (tDCS) on sleep and depressive symptoms in adults with moderate depression. tDCS is a noninvasive neuromodulation technique that delivers a mild electrical current to the scalp to modulate brain activity and has been studied as a potential treatment for depression. Participants will self-administer tDCS for 20 sessions at home over the course of the study. Sleep will be continuously monitored using a wearable device called an Oura Ring that captures sleep measures such as sleep duration, efficiency, awakenings, and night-to-night consistency. Depressive symptoms will be assessed longitudinally using validated clinical and self-report measures. The primary objective is to determine whether changes in sleep consolidation occur over the course of tDCS treatment. A secondary objective is to evaluate whether changes in sleep are temporally associated with improvements in depressive symptoms. This study aims to better characterize the relationship between sleep and depressive response during tDCS, and to identify potential sleep-related markers associated with clinical improvement in depression.