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Here Comes the Sun: Phototherapy and SAD
By Dónal P. O'Mathúna, PhD. Dr. O'Mathúna is Senior Lecturer in Ethics, Decision- Making & Evidence, School of Nursing, Dublin City University, Ireland; he reports no financial relationship to this field of study.
Source: Horowitz S. Shedding light on seasonal affective disorder. Altern Complement Ther 2008;14:282-287.
Hippocrates, the noted Greek physician, once said: "It is chiefly the changes of the seasons which produce diseases." And modern scientists also recognize this. Commonly known as winter depression, seasonal affective disorder (SAD) is classified as a mood disorder with a seasonally recurrent pattern. The well-known seasonal symptoms of depressed mood, low energy levels, disturbed sleep, overeating, and weight gain were first described in clinical terms in the early 1980s. This article discusses the prevalence, diagnosis, treatment options, and etiology of this disorder.
January brings a sense of relief in Ireland as the days are finally starting to lengthen. Things can get gloomy on those days when daylight is limited to six or seven hours. People living in more northern latitudes get even less daylight. For some, the lack of daylight is not just a nuisance but can trigger such severe changes in mood, energy, and appetite that they are diagnosed with seasonal affective disorder (SAD). This condition can include depression, lack of energy, disturbed sleep, loss of libido, overeating, and weight gain.1 To be characterized as SAD, the symptoms must develop during the fall and winter, decrease as the days lengthen, and be absent in the spring and summer. The symptoms have a wide range of severity.
The incidence of SAD is much higher in women than men. Various studies put the incidence at 3-4 times higher in women than men. However, both genders experience the same range of symptoms and appear to respond similarly to different therapies.2 The overall prevalence of SAD in the general population ranges from 4% to 10%. For unknown reasons, SAD is more prevalent in the northern hemisphere than the southern hemisphere.1 There may be some genetic component to the condition. For example, people of Icelandic descent living in Canada had a significantly lower incidence of SAD compared to people living in the same area of non-Icelandic descent.1
The Horowitz article focused primarily on reviewing the evidence available for therapies commonly used to treat SAD. The standard approach currently is bright light therapy using a light box with white fluorescent lights of 10,000 lux. This is about 20 times more intense than ordinary indoor lighting. Other practitioners recommend less intense light and there is some debate as to whether the intensity of the light impacts effectiveness.1 With the intense light, ultraviolet filters are usually attached to avoid harm to eyes or skin. People typically sit exposed to the light for 30 minutes each morning, increasing to twice daily as daylight shortens. Side effects rarely develop, but can include headaches, eye strain, irritation, insomnia, and other mild symptoms, which decrease as exposure is reduced. The review mentioned that light therapy was clinically validated, but only a few clinical studies were briefly described. A more complete description of the available studies and a critical appraisal of their findings would have been more beneficial.
A number of dietary supplements are also used during the treatment of SAD. These include vitamin D, melatonin, L-tryptophan, and 5-hydroxytryptophan. The review provided a very brief overview of some of the evidence available for their use, which appears to be inconclusive. In spite of this, the review cited various authorities who recommend the use of different supplements. A variety of pharmaceutical antidepressants have been used to treat SAD, either with or without concurrent light therapy. The review referenced clinical trials that have been conducted using these drugs for SAD, but did not critically appraise the primary literature.
Other approaches to SAD therapy include psychotherapy and lifestyle factors. Among the former, cognitive behavioral therapy has shown promise in some controlled trials. Patients had significantly better outcomes when cognitive behavioral therapy was used in addition to light therapy compared to light therapy alone. As would be expected, other lifestyle factors can impact people's mood. Approaches to treating SAD generally recommend regular exercise (in the outdoors if possible to increase light exposure), developing support through friends and family or a more structured support group, and using an activity diary to determine if other factors influence symptoms. The review did not discuss whether these approaches have been evaluated in studies.
The Horowitz review provides a useful introduction to SAD and the variety of approaches to its treatment. However, it suffers from the limitations of any narrative review as compared to a systematic review. No details are given as to why the cited studies were chosen over others, and the quality and details of the studies were not examined. The conclusions of practitioners and authorities in the field were cited without explaining how they evaluated the contradictory evidence often available from clinical studies. The article also would have benefitted from further examination of the diagnosis of SAD, and especially how it can be distinguished from other conditions with similar symptoms. The review should only be used as an introduction to the field. Further examination of the literature would be needed to provide the evidence necessary to influence practice in this area.
1. Miller AL. Epidemiology, etiology, and natural treatment of seasonal affective disorder. Altern Med Rev 2005;10:5-13.
2. Leibenluft E, Hardin TA, Rosenthal NE. Gender differences in seasonal affective disorder. Depression 1995;3:13-19.