The gloom of winter, more often a literary theme than a medical topic, is a biological reality for an estimated 10 million Americans who suffer from seasonal affective disorder (SAD). For some, however, the depression ushered in by the dark days of winter can be treated simply and with rapid results with 30 minutes to two hours of bright-light therapy per day for a few weeks.
Recently, the possible causes of and treatments for SAD were explored at a National Institute of Mental Health (NIMH) press briefing and in the Dec. 8, 1993, issue of JAMA.
At the press briefing, a panel of experts discussed the symptoms of SAD, its effects on 35 million Americans (10 million with SAD and 25 million with subsyndromal SAD or "winter blues") and the available treatments. Among the experts were Alan I. Leshner, Ph.D., deputy director of NIMH; Norman E. Rosenthal, M.D., chief of the section on environmental psychiatry, NIMH's Clinical Psychobiology Branch; and M. Lawrence Nicodemus, meteorologist, U.S. Department of Commerce's National Climatic Data Center.
NIMH conducted the briefing to focus attention on SAD's widespread prevalence and to encourage the medical community to take the disorder seriously and to recognize its scientific credibility.
"SAD is real and treatable," explained Leshner, who cited the JAMA article as a "milestone of recognition."
SAD has come to light as a widespread form of severe depression largely because of the efforts of Rosenthal, a psychiatrist, director of light therapy studies at NIMH and author of the JAMA article. Rosenthal, a native South African who came to NIMH as a researcher in the late 1970s, wrote Winter Blues, in which he chronicles for patients the discovery, diagnosis and treatment of SAD.
SAD is a clinical illness characterized by periods of depression that begin in October and subside in April. SAD symptoms in adults include lethargy, fatigue, ravenous appetite, weight gain, carbohydrate craving, withdrawal from relationships, inability to concentrate or focus, problems at work, anxiety and despair. Diagnosis is based on seasonality of symptoms determined in a patient history. Most (75 percent to 80 percent) of SAD sufferers are women, for whom the illness typically begins in the third decade of life. SAD also has been observed in children, who may exhibit signs of irritability, difficulty getting out of bed and problems in school, particularly during the fall and winter. The prevalence of SAD in the United States has been found to increase with increasing latitude and has been estimated to range from 1.4 percent in Florida to 9.7 percent in New Hampshire.
While climate, season and weather have historically been known to affect mood, only within the last decade have scientists documented and measured this effect, according to Nicodemus. In addition to latitude, storm patterns and cloud cover contribute to winter dreariness and exacerbate SAD in some parts of the country, particularly the Great Lakes region. People living in the Southeast and Southwest have twice as much sunshine in winter as people in Northern states, he said.
The threshold of light that elicits depression varies for individuals, Rosenthal said. One person may develop SAD in Maryland but not in Florida. Another may become depressed in Maine but not in Maryland.
A female SAD patient who attended the NIMH meeting told Psychiatric Times of her 10-year use of light therapy and her sensitivity to light variation. Although aware of her vulnerability, she apparently enjoyed testing her limits. With a sense of humor, she told of her cruises to see the Arctic's midnight sun and to the tip of South America during the Southern Hemisphere's winter. During the trips she recorded a mood log that revealed her rapid mood swings as the cruise ships' routes created dramatic seasonal changes.
Treatment is based on the interaction of light with the eyes, not the skin, Rosenthal said. Imagining light during meditation has no effect. Light therapy regulates brain chemistry by controlling the levels of the neurotransmitter serotonin and the hormone melatonin, Rosenthal believes. While serotonin regulation may be abnormal, its abnormality seems to be a decreased responsiveness to light that can be corrected with more light, said Rosenthal. The light effect is probably transmitted via the nerve tract that connects the retina to the hypothalamus' suprachias-matic nuclei, considered the body's biological clock. He hypothesizes that SAD patients, with a couple of weeks of insufficient light, produce inadequate serotonin, which leads to their depression. Light therapy increases serotonin production.
In a recent article in the Journal of Biological Psychiatry, Rosenthal and his coworkers documented an exaggerated behavioral response in SAD patients administered an experimental serotonin agonist (m-CPP). SAD patients had increased activation and euphoria. This also correlated with SAD patients' reported activation following a high-carbohydrate meal. In contrast, control subjects report feeling sedated. The "aberrant response may reflect serotonergic dysregulation...and may reflect a behavioral attempt to normalize this putative serotonergic abnormality," Rosenthal and coauthors wrote.
1. Rosenthal NE. Diagnosis and treatment of seasonal affective disorder. JAMA. Dec. 8, 1993; 270:2717-2720.
2. Rosenthal NE. Winter Blues. New York: Guilford Press; 1993.
3. Rosenthal NE, et al. Seasonal variation in behavioral responses to m-CPP in patients with seasonal affective disorder and controls. J Biol Psychiatry. 1993;33:496-504.