A single 30-minute walk on a treadmill can give a temporary emotional lift to patients diagnosed with major depressive disorder, the results of a small study suggest.

Researchers found that among 40 men and women recently diagnosed with major depression, those who spent just a half hour on a treadmill reported a short-term improvement in energy and emotional well-being.

Though a single workout is not the answer to clinical depression, the researchers say, exercise could offer depressed patients a way to give themselves an emotional boost.

“If you can go out and walk and get the recommended amount of exercise, then it might help you manage your symptoms on a day-to-day basis,” said lead study author Dr. John Bartholomew of the University of Texas at Austin.

Past studies, he explained in an interview, have shown that regular exercise can help treat depression over time. But the new findings show that “you don’t have to wait” to start getting some benefit, he said.

Bartholomew and his colleagues report their findings in the journal Medicine & Science in Sports & Exercise.

A number of studies have found that active adults are less likely to suffer depression than their sedentary peers, while some clinical trials have shown regular exercise can serve as a therapy for the disorder - and perhaps be as effective as antidepressant drugs in some cases.

But the immediate effects of exercise on depressed individuals have been unclear.

Patients in the current study were randomly assigned to walk on a treadmill for 30 minutes or spend the time resting quietly in a comfortable chair. All completed standard surveys of mood and well-being before and after their exercise or rest period.

The researchers found that both exercise and quiet rest appeared to boost patients’ mood, helping them feel less fatigue, tension, distress and anger.

But the exercisers reported greater gains in general well-being and “vigor,” the study found.

According to Bartholomew, the quiet-rest group may have felt better just because they were getting out of the house and interacting with others. People with depression, he noted, often isolate themselves and avoid social situations, which can in turn feed the depression.

Experts have speculated that exercise aids depression, in part, through direct physiological effects. For example, physical activity seems to affect some key nervous system chemicals - norepinephrine and serotonin - that are targets of antidepressant drugs, as well as brain neurotrophins, which help protect nerve cells from injury and transmit nerve signals in brain regions related to mood.

But Bartholomew said there may be “cognitive” effects at work. Exercisers in this study, he explained, may have felt a “sense of accomplishment” that lifted their general mood.

One of the challenges to using exercise as depression therapy is that the condition makes it hard for people to find the motivation to be active, Bartholomew noted. But if they can get outside for even a short walk, he said, it could help in managing the daily symptoms of the disorder.

SOURCE: Medicine & Science in Sports & Exercise, December 2005.