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. 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 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. 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.
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.