Major depression is a highly prevalent, chronic, and debilitating mental health problem with significant social cost that poses a tremendous economic burden. Winter seasonal affective disorder (SAD) is a subtype of recurrent major depression involving substantial depressive symptoms that adversely affect the family and workplace for about 5 months of each year during most years, beginning in young adulthood. This clinical trial is relevant to this public health challenge in seeking to develop and test a time-limited (i.e., acute treatment completed in a discrete period vs. daily treatment every fall/winter indefinitely), palatable cognitive-behavioral treatment with effects that endure beyond the cessation of acute treatment to prevent the annual recurrence of depression in SAD.

Aim (1) To compare the long-term efficacy of cognitive-behavioral therapy (CBT) and light therapy on depression recurrence status, symptom severity, and remission status during the next winter season (i.e., the next wholly new winter season after the initial winter of treatment completion), which we argue to be the most important time point for evaluating clinical outcomes following SAD intervention.

Hypothesis: CBT will be associated with a smaller proportion of depression recurrences, less severe symptoms, and a higher proportion of remissions than light therapy in the next winter. The study is designed to detect a clinically important difference between CBT and light therapy in depressive episode recurrences during the next winter, the primary endpoint, in an intent-to-treat analysis.

Aim (2) To compare the efficacy of CBT and light therapy on symptom severity and remission status at post-treatment (treatment endpoint).

Hypothesis: CBT and light therapy will not differ significantly on post-treatment outcomes.

Seasonal affective disorder (SAD) is a subtype of recurrent depression involving major depressive episodes during the fall and/or winter months that remit in the spring. SAD affects an estimated 5% of the U. S. population, over 14.5 million Americans. The central public health challenge in the management of SAD is prevention of winter depression recurrence. The established and best available treatment, light therapy, remits acute symptoms in 53% of SAD cases. However, long-term compliance with clinical practice guidelines recommending daily use of a light box from onset of first symptom through spontaneous springtime remission during every fall/winter season is poor. Time-limited alternative treatments with durable effects are needed to prevent the annual recurrence of these disabling symptoms. Our preliminary studies suggest that a novel, SAD-tailored cognitive-behavioral therapy (CBT) may be as efficacious as light therapy alone for acute SAD treatment and that CBT may have superior outcomes to light therapy during the next winter. During the next wholly new winter season following the initial winter of study treatment, the proportion of depression recurrences was significantly smaller in participants randomized to CBT (5.8%) or to CBT combined with light therapy (5.2%) than in participants randomized to light therapy alone (39.2%). As the next step in this programmatic line of intervention studies, the primary aim of the proposed project is to further test the efficacy of our CBT for SAD intervention against light therapy in a larger, more definitive randomized head-to-head comparison on next winter outcomes in an intent-to-treat (ITT) analysis using all randomized participants. This project is seeking to test for a clinically meaningful difference between CBT and light therapy on depression recurrence in the next winter (the primary outcome), thereby having the potential to impact clinical practice. The proposed work will go beyond our pilot studies in four ways: (1) This study will augment the generalizability of our prior pilot study data by relaxing the inclusion/exclusion criteria to allow for comorbid diagnoses and stable antidepressant medication use and by demonstrating the feasibility of training experienced community therapists to facilitate the CBT groups. (2) We will prospectively track recurrences and potential intervening variables that could affect outcome (e.g., new treatments, summer remission status) in the interim between treatment endpoint and the following winter. (3) This study includes a second annual winter followup to obtain preliminary data on the comparative effects of CBT vs. LT two winters after the initial winter of study treatment. (4) We will examine how potential modifiers influence the effects of CBT vs. LT, including demographic variables; baseline characteristics (e.g., depression severity, comorbidity, baseline medication status); and complete or incomplete summer remission status in the interim. If successful, this work will develop a novel treatment with important public health implications for winter depression prevention.

Inclusion Criteria:

• aged 18 or older
• meet DSM-IV criteria for Major Depression, Recurrent, with Seasonal Pattern
• meet Structured Interview Guide for the Hamilton Rating Scale for Depression-Seasonal Affective Disorder Version (SIGH-SAD) criteria for a current SAD episode

Exclusion Criteria:

• past light therapy or cognitive-behavioral therapy for SAD
• presence of a comorbid Axis I disorder that requires immediate treatment
• acute and serious suicidal intent
• positive laboratory findings for hypothyroidism
• plans for major vacations or absences from the study area through March