Seasonal Affective Disorder and Beyond

Abstract

Seasonal affective disorder (SAD) is a mood disorder characterized by atypical symptoms of depression (depressed mood, hypersomnia, hyperphagia, and weight gain). It usually begins in the fall or winter and remits during the spring. Five percent to 6% of the U.S. population suffer from full-blown SAD with an additional 15% afflicted with subsyndromal SAD. The prevalence of SAD increases with increasing distance from the equator. The first published report on the use of bright light to treat SAD appeared in 1982. Subsequent controlled studies have, for the most part, confirmed the efficacy of bright light treatment for SAD. Fifty percent to 60% of patients show a robust response within 4 or 5 days of beginning treatment. The editor solicited contributions from experts in the field of bright light therapy and had each of them summarize and report their findings in separate chapters. The book is comprehensive. Some chapters, such as the one on biological and physical properties of light, may not be of immediate concern to the primary care physician, but the editor has done such a superb job of organizing the book that the reader will be able to quickly pick out the chapters and sections of greatest relevance. The physician will probably find the information on bright light treatment of SAD, nonseasonal major depression, premenstrual dysphoria, and bulimia to be of most interest. Some physicians may also want to scan the chapters on the use of light to treat sleep phase disorders, jet lag, problems associated with shift work, and insomnia in older patients. The contributors provide convincing evidence that bright light is a viable first-line treatment for all of these conditions. A few quibbles: Several studies on the use of bright light therapy in the treatment of bipolar depression are mentioned in the chapter on nonseasonal major depression, but are not referenced in the index. The omission is surprising since the first published report on the efficacy of light therapy was with a bipolar patient.1 In addition, many patients with winter SAD are mildly bipolar. It would also have been helpful if the editor and publisher had included in the index a reference to the use of bright light to extend the antidepressant effects of partial sleep deprivation. This is an excellent resource for the primary care physician interested in learning about or using bright light therapy.