ABSTRACT FROM: Rohan KJ, Mahon JN, Evans M, et al. Randomized trial of cognitive-behavioral therapy versus light therapy for seasonal affective disorder: acute outcomes. Am J Psychiatry 2015;172(9):862–9.
What is already known on this topic?
The overall lifetime prevalence of seasonal affective disorder (SAD) ranges as high as 9.7%.1 Light therapy, where bright artificial light is used to replace diminished sunlight, can be an effective non-drug treatment for SAD.2 However, alternative non-drug treatment approaches are also needed. Cognitive behavioural therapy (CBT) is an established and effective treatment for depressive disorders.3 Limited research examining CBT adapted specifically for SAD (CBT-SAD) is available.
Methods of the study
This paper reports initial findings from a large 5-year randomised clinical trial funded by the National Institute of Mental Health and conducted in Burlington, Vermont. In 2006, over a 6-week period during the winter solstice, 177 adults with a current episode of depression that was recurrent with a seasonal pattern were treated with either two weekly sessions of 90 min CBT-SAD therapy (N=88), or daily 30 min exposures to 10 000–lux cool-white florescent light each morning (N=89). Inclusion criteria included screening for SAD with the Structured Clinical Interview for DSM-IV (SCID); the Structured Interview Guide for the Hamilton Rating Scale for Depression-SAD Version (SIGH-SAD) and no stable use of antidepressants. Exclusion criteria included current or prior use of light therapy; a comorbid axis I disorder requiring immediate treatment; suicidal intent; hypothyroidism; or plans to be absent for more than a week. The SIGH-SAD was administered by a blind rater before treatment, at weeks 1–5 and after treatment. SIGH-SAD-derived outcomes included total score (range=0–90), scores on its component subscales and remission status after treatment. The Beck Depression Inventory—Second Edition (BDI-II), a 21-item self-report measure of depressive symptom severity, was administered before treatment, at week 3 and after treatment. To examine change in depression severity on the SIGH-SAD across the 6 weeks of treatment, mixed-effects regression models with treatment (CBT-SAD or light therapy), time (pretreatment, weeks 1–5 and post-treatment) and their interaction as fixed effects, and subject as a random effect, were used. The intent-to-treat sample included 177 fully eligible patients who were randomly assigned to CBT-SAD (N=88) and light therapy (N=89). No patient was withdrawn because of adverse effects, and no harmful or unintended effects were observed in either treatment group. However, one participant (of 89, 1.1%) voluntarily withdrew from light therapy, and 13 of 88 participants (14.7%) withdrew from CBT-SAD.
What does this paper add?
Outcome scores on the SIGH-SAD and Beck Depression Inventory–Second Edition (BDI-II) revealed that CBT-SAD and light therapy were comparably effective for SAD during an acute episode. CBT-SAD and light therapy did not differ in remission rates based on the SIGH-SAD (47.6% vs 47.2%, respectively) or the BDI-II (56.0% vs 63.6%).
Professionals and the lay public alike are becoming more aware that SAD exists and that non-drug treatment approaches are beginning to show promise. By comparing a relatively newer approach (CBT-SAD) with a more established approach (light therapy), this study introduces a new way of thinking about SAD. With CBT-SAD, the approach is active in that clients learn how to change their behaviour. However, with light therapy, clients passively use a light box.
Using a large sample size, setting statistical power at 80%, implementing a randomised clinical trial methodology and extending the investigations over several years all lend important credibility to the research. No previous studies comparing CBT-SAD and light therapy are available.
The CBT-SAD approach developed by the researchers is unique. Given that current options for treating SAD often focus on medications and or light therapy, CBT-SAD will be of interest to other professionals who treat SAD.
Limitations
Participants were from the same geographical area and this may limit the generalisability of the findings.
CBT-SAD protocols implemented with individuals living in an urban Vermont community may not be relevant to those in rural areas; or to those living in areas farther from the equator, where winter daylight hours are shorter.
In 2015, reporting findings from a study conducted in 2006 suggests considerable lag time.
Training for and supervision of the unique CBT-SAD treatment protocol was extensive, possibly making it difficult for other professionals to implement.
What next in research?
Future studies should consider qualitative research that explores individuals' experiences with SAD; aspects of the CBT-SAD treatment that was especially meaningful to them; and the kinds of personalised treatment plans they created during their therapy.
Do these results change your practices and why?
Not yet (and probably not everywhere). Effective non-drug treatment approaches, such as the CBT-SAD protocol trialled in this study, have the potential to bring needed relief to individuals living with SAD. However, information related to replicating the specific treatment protocols is not yet available. At present, professional training for implementing CBT-SAD treatment groups is available only in the researchers' geographical area. As the programme of research developing and evaluating these unique protocols continue, incorporating more training opportunities for professionals will increase the relevance of the results to practice.
Footnotes
Competing interests: None declared.
Provenance and peer review: Commissioned; internally peer reviewed.
References
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