In 1984, Dr. Rosenthal, then of the National Institute of Mental Health, published a groundbreaking article about the seasonal pattern of depression and bipolar disorder; he also coined the term “Seasonal Affective Disorder” (SAD). Seasonal Affective Disorder is today described in the DSM-IV as a “regular temporal relationship” between the onset of major depression and the time of year (fall or winter), accompanied by a full remission (or change to mania or hypomania) in the spring.
Dr. Rosenthal reported on the positive reactions of depressed patients when they were exposed to bright light therapy on a daily basis in fall and winter days: their symptoms of depression improved.
Since persons who have bipolar disorder often slide into autumnal and winter slumps, close monitoring of this potential pattern of annual relapse needs to be documented. Usually, if a pattern is recognized, the occurrence repeats itself, sometimes to within a week, from year to year. Light therapy tends to work better as a preventive treatment; so knowing the periods of vulnerability affords an opportunity to intervene in advance.
What are light boxes?
A light box is a metal fixture approximately two feet long and one and a half feet high. It contains ordinary white fluorescent light bulbs set behind a plastic diffusing screen, which becomes a film that filters out most of the ultraviolet (UV) rays from the bulbs.
Typically, the light emitted from these boxes varies between 2,000 to 10,000 lux in intensity. (Lux is a unit used to measure the intensity of light. Indoor light levels range from 200 to 700 lux; outdoor levels on a sunny spring day range from 2,000 to well beyond 10,000 lux.)
A person should sit approximately one to two feet from the light source at a 45 degree angle and look up for a few seconds toward the light every several minutes or so.
Initially, one has to be cautious about reaching an effective daily duration of exposure—usually 20 to 30 minutes. Rarely, fewer than 10 minutes of exposure may trigger a brief period of activation that is readily diminished by reducing the duration of exposure.