Why is this review important?
Many people in northern latitudes suffer from seasonal affective disorder (SAD), which occurs as a reaction to reduced sunlight. Three-quarters of those affected are women. Lethargy, overeating, craving for carbohydrates and depressed mood are common symptoms. In some people, SAD becomes a depression that seriously affects their daily lives. Up to two-thirds experience depressive symptoms every winter.
Who might be interested in this review?
Anyone who has experienced SAD or who has relatives and friends who have experienced SAD, as well as researchers working in this field might be interested in this review.
What questions does this review aim to answer?
The predictable seasonal aspect of SAD provides a promising opportunity for prevention. However, little is known about the efficacy and potential harms of interventions for preventing SAD. This is one of four reviews conducted to examine the efficacy and side effects of interventions used to prevent SAD; this review focuses on psychological therapy as a preventive intervention in people with a history of SAD who were free of symptoms at the time the preventive intervention was started.
Which studies were included in the review?
We searched databases up to 19 June 2018 for studies on psychological therapies to prevent SAD. Among 3745 records, we found one randomised controlled study including 46 people who received a form of psychological therapy - the so called mindfulness-based cognitive therapy (MBCT) or treatment as usual. Treatment as usual meant that participants did not receive any preventive treatment but were invited to start light therapy as first depressive symptoms occurred. All individuals in these studies had a history of winter depression and were free of depressive symptoms when the study started.
What does evidence from this review reveal?
The proportion of participants developing a depression in the upcoming winter was similar in both groups as well as the severity of these depressive episodes. However, the quality of the evidence was very low, so we can draw no valid conclusion if MBCT is really ineffective in preventing SAD or not. The included study reported no information on side effects of the intervention. Doctors need to discuss with patients the advantages and disadvantages of MBCT and other potentially preventive treatments for winter depression, such as other psychological therapies, drug treatments, or lifestyle interventions. As no available studies have compared these treatments, treatment selection should be strongly based on patient preferences and other preventive interventions that are supported by evidence.
What should happen next?
Review authors recommend that future studies should evaluate the efficacy of different psychological therapies in preventing SAD in larger study samples and should directly compare these interventions versus other preventive treatments, such as light therapy, antidepressants and agomelatine, to determine the best treatment option for prevention of SAD.
The evidence on psychological therapies to prevent the onset of a new depressive episode in people with a history of SAD is inconclusive. We identified only one study including 46 participants focusing on one type of psychological therapy. Methodological limitations and the small sample size preclude us from drawing a conclusion on benefits and harms of MBCT as a preventive intervention for SAD. Given that there is no comparative evidence for psychological therapy versus other preventive options, the decision for or against initiating preventive treatment of SAD and the treatment selected should be strongly based on patient preferences and other preventive interventions that are supported by evidence.
Seasonal affective disorder (SAD) is a seasonal pattern of recurrent major depressive episodes that most commonly occurs during autumn or winter and remits in spring. The prevalence of SAD ranges from 1.5% to 9%, depending on latitude. The predictable seasonal aspect of SAD provides a promising opportunity for prevention. This is one of four reviews on the efficacy and safety of interventions to prevent SAD; we focus on psychological therapies as preventive interventions.
To assess the efficacy and safety of psychological therapies (in comparison with no treatment, other types of psychological therapy, second-generation antidepressants, light therapy, melatonin or agomelatine or lifestyle interventions) in preventing SAD and improving person-centred outcomes among adults with a history of SAD.
We searched Ovid MEDLINE (1950- ), Embase (1974- ), PsycINFO (1967- ) and the Cochrane Central Register of Controlled Trials (CENTRAL) to 19 June 2018. An earlier search of these databases was conducted via the Cochrane Common Mental Disorders Controlled Trial Register (CCMD-CTR) (all years to 11 August 2015). Furthermore, we searched the Cumulative Index to Nursing and Allied Health Literature, Web of Science, the Cochrane Library, the Allied and Complementary Medicine Database and international trial registers (to 19 June 2018). We also conducted a grey literature search and handsearched the reference lists of included studies and pertinent review articles.
To examine efficacy, we included randomised controlled trials (RCTs) on adults with a history of winter-type SAD who were free of symptoms at the beginning of the study. To examine adverse events, we intended to include non-randomised studies. We planned to include studies that compared psychological therapy versus no treatment, or any other type of psychological therapy, light therapy, second-generation antidepressants, melatonin, agomelatine or lifestyle changes. We also planned to compare psychological therapy in combination with any of the comparator interventions listed above versus no treatment or the same comparator intervention as monotherapy.
Two review authors screened abstracts and full-text publications against the inclusion criteria, independently extracted data, assessed risk of bias, and graded the certainty of evidence.
We identified 3745 citations through electronic searches and reviews of reference lists after deduplication of search results. We excluded 3619 records during title and abstract review and assessed 126 articles at full-text review for eligibility. We included one controlled study enrolling 46 participants. We rated this RCT at high risk for performance and detection bias due to a lack of blinding.
The included RCT compared preventive use of mindfulness-based cognitive therapy (MBCT) with treatment as usual (TAU) in participants with a history of SAD. MBCT was administered in spring in eight weekly individual 45- to 60-minute sessions. In the TAU group participants did not receive any preventive treatment but were invited to start light therapy as first depressive symptoms occurred. Both groups were assessed weekly for occurrence of a new depressive episode measured with the Inventory of Depressive Syptomatology-Self-Report (IDS-SR, range 0-90) from September 2011 to mid-April 2012. The incidence of a new depressive episode in the upcoming winter was similar in both groups. In the MBCT group 65% of 23 participants developed depression (IDS-SR ≥ 20), compared to 74% of 23 people in the TAU group (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.60 to 1.30; 46 participants; very low quality-evidence).
For participants with depressive episodes, severity of depression was comparable between groups. Participants in the MBCT group had a mean score of 26.5 (SD 7.0) on the IDS-SR, and TAU participants a mean score of 25.3 (SD 6.3) (mean difference (MD) 1.20, 95% CI -3.44 to 5.84; 32 participants; very low quality-evidence).
The overall discontinuation rate was similar too, with 17% discontinuing in the MBCT group and 13% in the TAU group (RR 1.33, 95% CI 0.34 to 5.30; 46 participants; very low quality-evidence).
Reasons for downgrading the quality of evidence included high risk of bias of the included study and imprecision.
Investigators provided no information on adverse events. We could not find any studies that compared psychological therapy with other interventions of interest such as second-generation antidepressants, light therapy, melatonin or agomelatine.