By Camille Chatterjee, published on September 1, 1997 - last reviewed on June 14, 2012
Seasonal affective disorder has a particularly apt acronym: In the fall andwinter months, lack of sunlight leaves those afflicted with SAD feeling gloomy, tired, and irritable. But their mood may not be all that suffers. Cognitive processes like memory may also be impaired--and these mental malfunctions seem resistant to light therapy, the main weapon against SAD.
Gail Eskes, Ph.D., and her colleagues at Canada's Dalhousie University found that SAD sufferers were less able to follow through on their everyday intentions and plans. Also impaired were visual memory and construction (visual memory helps us recall an object's location; visual construction lets us draw an object that we're viewing).
With the coming of summer or exposure to light therapy, a SAD sufferer's depression usually lifts. But visual memory and construction problems seem to resist both therapy and the sun, while difficulties in completing goals persist through therapy but improve in the summertime. Eskes speculates that these mental blocks could actually be caused by the lack of motivation that is often associated with SAD, or by central nervous system dysfunction. In any case, she says, there's a lot more to SAD than feeling low.