# Optimizing Long-Term Outcomes for Winter Depression with CBT-SAD and Light Therapy: Confirming the Targets, Mechanisms, and Treatment Sequence

> **NIH NIH R01** · UNIVERSITY OF VERMONT & ST AGRIC COLLEGE · 2020 · $812,936

## Abstract

Winter seasonal affective disorder (SAD) is a subtype of recurrent depression involving major
depressive episodes during the fall and/or winter months that remit each spring. The central
public health challenge in the management of SAD is prevention of winter depression
recurrences. This application focuses on two SAD treatments that each work for some patients:
light therapy (LT) and a SAD-tailored group cognitive-behavioral therapy (CBT-SAD). LT is the
acute SAD treatment with the most substantial evidence to support its efficacy. Correction of
circadian phase is LT's established target and mechanism. In our recently completed R01-level
efficacy trial, post-treatment outcomes for CBT-SAD and LT were very similar, but CBT-SAD
was associated with fewer depression recurrences over 2-year followup than LT (27.3% in CBT-
SAD vs. 45.6% in LT). CBT-SAD engaged and altered a specific mechanism of action, seasonal
beliefs, which improved at twice the rate during CBT-SAD compared to LT, and this
improvement was associated with lower risk for recurrence following CBT-SAD. This
confirmatory efficacy R01 will apply the experimental therapeutics approach to determine how
each treatment works when it is effective and to identify the best candidates for each. We will
ascertain whether theoretically-derived candidate biomarkers of each treatment's target and
effect are prescriptive of better outcomes in that treatment vs. the other. Biomarkers of LT's
target and effect include circadian phase angle difference (PAD) and the post-illumination pupil
response (PIPR). Biomarkers of CBT-SAD's target and effect include pupil dilation and
sustained gamma band EEG responses to seasonal words, which are hypothesized to reflect
less engagement with seasonal stimuli following CBT-SAD and corroborate with the established
target of seasonal beliefs. In addition to determining change mechanisms, we will test the
efficacy of a “switch” decision rule upon recurrence to inform clinical decision-making in
practice. We will randomize 160 adults with SAD to 6-weeks of CBT-SAD or LT in Winter 1;
follow subjects in Winter 2; and, if a depression recurrence occurs, cross them over into the
alternate treatment (i.e., switch from LTCBT-SAD or CBT-SADLT). All subjects will be
followed in Winter 3. Biomarker assessments will occur at pre- and post-treatment in Winter 1,
at Winter 2 followup (and again at post-treatment for those crossed-over), and at Winter 3
followup. Consistent with NIMH's priorities for demonstrating target engagement at the level of
RDoC-relevant biomarkers, this work aims to confirm the targets and mechanisms of LT and
CBT-SAD to maximize the impact of future dissemination efforts.

## Key facts

- **NIH application ID:** 9872203
- **Project number:** 5R01MH112819-03
- **Recipient organization:** UNIVERSITY OF VERMONT & ST AGRIC COLLEGE
- **Principal Investigator:** KELLY J. ROHAN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $812,936
- **Award type:** 5
- **Project period:** 2018-05-01 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9872203

## Citation

> US National Institutes of Health, RePORTER application 9872203, Optimizing Long-Term Outcomes for Winter Depression with CBT-SAD and Light Therapy: Confirming the Targets, Mechanisms, and Treatment Sequence (5R01MH112819-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9872203. Licensed CC0.

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