Sizing up SADness according to latitude.

Sizing up SADness according to latitude

For eight years, psychiatrists have studied small groups of people suffering from depressions that recur in either winter or summer. It now appears that at least 4 percent of the population living at middle latitudes suffers from seasonal depression.

"This is a much more common problem than we thought several years ago," says Norman E. Rosenthal of the National Institute of Mental Health in Bethesda, Md., a coauthor of the report in the September ARCHIVES OF GENERAL PSYCHIATRY.

In a random sample of 416 adults contacted by telephone in Montgomery County, Md. (just outside Washington, D.C.), 18 people reported symptoms of recurring winter depression and three fulfilled criteria for summer depression. Personal interviews with 40 of the respondents yielded four cases of winter depression. Psychiatrists refer to these depressions as seasonal affective disorder, or SAD.

If the prevalence estimate accurately reflects Montgomery County's population, more than 22,000 of its residents contend with SAD.

Some investigators say winter SAD can occur from fall through winter. The new study focuses on people who feel the worst in January and February. Symptoms include a marked drop in mood, lack of energy, oversleeping, overeating and carbohydrate craving. Summer SAD peaks in July and August. Its characteristic symptoms include agitation, insomnia and appetite loss.

There were significantly more cases of SAD among women 21 to 40 years of age than in any other group, the researchers note, a finding consistent with the higher prevalence of nonseasonal depression among young women.

Another 56 respondents reported milder but noticeable symptoms of winter and summer SAD. The scientists, led by Siegfried Kasper of the University of Bonn, West Germany, conclude that SAD represents the extreme end of a spectrum of seasonal mood and behavior changes affecting a substantial minority of the population.

According to the researchers, nearly half the respondents in Montgomery County had heard or read about SAD, which may have led to an overreporting of seasonal symptoms in this well-educated community. But further studies tend to support the prevalence estimate, Rosenthal asserts.

"There is an increase in the prevalence of SAD with increases in latitude," he adds.

In an unpublished study, Rosenthal and his co-workers evaluated about 1,400 questionnaires filled out by patients visiting physicians' offices in Florida, Maryland, New York and New Hampshire. SAD symptoms were reported by 1.4 percent of the Floridians, 6.3 percent of those living in Maryland, about 8 percent of the New Yorkers and nearly 10 percent of New Hampshire residents.

The prevalence of mild SAD symptoms ranged from 2.6 percent in Florida to 11 percent in New Hampshire.

Preliminary results from a study conducted by another researcher suggest 9 percent of the population in Alaska has winter SAD, and as many as one out of five Alaskans suffers from milder symptoms of the disorder.

Some psychiatrists claim that SAD is not a discrete disorder, but rather a collection of symptoms seen in people with other types of depression.

"It's valid to ask to what degree SAD is separable from other psychiatric syndromes," Rosenthal says. But clear cases of recurring, seasonal depression have emerged in the last eight years of research, he maintains. Long-term studies of SAD patients, who often feel better after sitting in front of bright lights (SN: 5/21/88, p.331), are now being planned.