HOLLYWOOD, Fla.

The line between depression and a well-adjusted senior life might literally be a step away.

Walking, stretching, lifting weights and low-impact aerobics are just some methods senior citizens are using not only to keep in shape but also to fight depression, one of the most-common conditions among elders.

"Exercising keeps them physically well and they don't feel as depressed," says Dr. Elizabeth Crocco, a geriatric psychiatrist and professor at the University of Miami School of Medicine. "And it's very helpful because it gets them out of the house."

She usually recommends walking and water exercises as part of depression treatment.

Depression involves a down mood and feelings of loneliness, sadness and unhappiness. The National Institute of Mental Health says that 19 million Americans suffer from it, 39 percent of them older than 45.

If untreated, depression can lead to suicide. About 60 to 75 percent of suicides among people age 75 and older can be traced to diagnosable depression.

Exercising is known for helping reduce mild to moderate depression because it stimulates the production of endorphins, an anti-depressant released in the brain that provokes the feeling of satisfaction and wellness.

This year, a study at Duke University reemphasized the advantages of physical exercise in the fight of depression, comparing for the first time the effects of anti-depressant drugs and exercise.

The study compared three groups of middle-aged to elderly people diagnosed with clinical depression.

One group attended a 45-minute exercise class three times a week, including 30 minutes of brisk walking or jogging. A second one received an anti-depressant and a third one took the medication and participated in the exercise classes.

The result: all three groups showed roughly the same improvement, though the one with medication and exercise showed improvement a bit faster.

In other research, the National Academy on an Aging Society shows that 57 percent of 51- to 61-year-olds who are well-adjusted engage in light exercise at least three times a week, compared to 32 percent of same-age seniors who were depressed.

But there is more to exercising than just its chemical benefits. For a lot of senior citizens, exercising is the best opportunity they have to leave the house and be around other people.

"Socialization is the most important thing in depression," said Carol Winter, a health support coordinator at the Southeast Focal Point Senior Center in Hollywood, Fla. "Just being out of their homes and coming to different activities helps them."

Winter teaches 30-minute exercise classes offered at the center, with an attendance of about 20 people.

Toni Lawrence says exercising helped her overcome depression after her husband.

At the time, the Hollywood senior citizen had been helping others for nine years with her low impact aerobics classes. However, it was only when she personally felt there was no reason to get up in the morning that she realized the importance of her classes.

"It helped me a lot," she says. "Now I don't have time to be depressed. I'm busy, busy, busy all the time."

Lawrence now works as an exercise instructor in various senior centers in Hollywood and Pembroke Pines, Fla. Her daily one-hour classes include light weightlifting, floor and low-impact exercises and meditation.

The elderly must also exercise their minds, says Irene Zwetch-kenbaum, a social worker at Southeast Focal Point who got her master's degree after she was a senior citizen.

Besides coordinating a depression support group, she also leads discussions of current events that somehow impact their lives. She said it helps them not focus so much on the things that make them depressed.

Winter says she tries to use different parts of the body in her classes.

And she has one special exercise at the end of the class that works various muscles at the same time, but that is the easiest of all: laughing.