How to avoid seasonal depression, according to the expert who discovered it

For millions of people, the shorter, darker days leading into winter also portend a darkening of their mood.

Many have seasonal affective disorder (SAD), a type of depression typically beginning in the fall or winter and marked by lower moods, lethargic energy, diminished pleasure and excessive sleepiness that affects an estimated 5 percent of Americans. Women are four times more susceptible to developing SAD. Many more people are believed to experience a milder version, known as the “winter blues.”

“If you are one of those people who really feel it and feel badly, you’ve got a lot of company and there’s a lot you can do about it,” said Norman Rosenthal, a psychiatrist at Georgetown University School of Medicine.

Rosenthal would know: He, along with his colleagues, first described and n