ABSTRACT The most common treatments for depression are antidepressant medications (ADs) and psychotherapies such as cognitive behavioral therapy (CBT). However, these treatments yield only moderate benefits under ideal circumstances. These effects are further eroded when real world patients initiate treatments at low rates and have poor adherence or early discontinuation. This represents a depression care gap that supports the development and promotion of other interventions. One of these alternative treatments, bright light therapy (BLT), has established efficacy for seasonal affective disorder (SAD) and non-SAD depression, is relatively low cost, and has few adverse effects—but is often overlooked and has little presence in routine clinical care. This R34 application is in preparation for a subsequent large, pragmatic trial to examine the effectiveness of bright light therapy (BLT) for depression when delivered to real-world patients with little “scaffolding” typical of highly controlled efficacy trials. We will conduct a feasibility pilot with a sample of 90 patients selected with a new clinical diagnosis of unipolar depression or SAD, or a PHQ-9 score >= 10, recorded in the healthplan’s electronic health record (EHR). Participants will be randomized to either: Arm 1: Treatment as Usual (TAU): A “usual care services” control group (e.g., ADs, psychotherapy; all TAU is permitted and will be recorded for all participants in all conditions); Arm 2: TAU + Minimal BLT Encouragement: TAU plus two minimal written communications (mailed letter, secure EHR message) promoting BLT as a promising treatment and outlining steps for patients to self-initiate; Arm 2 will not include any phone coaching or adherence promotion; or Arm 3: TAU + Enhanced BLT Encouragement + Adherence Promotion: TAU plus 2-4 brief calls to encourage BLT use, advise on purchase of a light box (LB), assist with obtaining insurance reimbursement, educate for correct LB use, and provide motivational interviewing (MI) as needed to promote adherence. The primary outcome is PHQ-9 self-reported depression symptoms; the primary test of BLT effectiveness is the contrast between Arms 2+3 vs. Arm 1. We will conduct exploratory analyses to prepare for a future fully-powered trial. We will examine other secondary outcomes including anxiety, disability, and mood seasonality, and other secondary contrasts; e.g., Arm 2 vs Arm 3. We will also examine moderation effects; variation of BLT effects in subgroups (e.g., those receiving vs. not receiving TAU antidepressants); and we will examine mechanisms of BLT and MI intervention effects via candidate mediators including normalized circadian rhythm, improved sleep, and increased physical activity (for BLT), and readiness for change (for MI). This pilot will yield feasibility products to assist with successful conduct of a subsequent full trial: estimates of recruitment success, participant retention, and adherence with BLT protocol; refinement of the ad...