MINNEAPOLIS - Life changed for Reed Steele five years ago when a series of injuries kept him from competing for his college cross country and track teams.

Unable to run, he got depressed. He turned to drugs and alcohol, hoping they could provide the escape that running had. Before long, his depression deepened until he was hospitalized and suicidal.

Today the 25-year-old feels better, thanks to a combination of antidepressants, therapy and exercise - a combination of swimming, cycling and moderate running.

"Exercise is extremely important for mental health," said Steele, of Roseville, a Twin Cities suburb. "When I was really depressed I wasn't exercising. ... I didn't have any desire to do anything."

Although there's no definitive research showing exercise by itself can cure depression, many mental health experts agree that it has positive mental benefits and can be a useful tool in overall therapy.

Depression is a serious illness thought to be related to chemical imbalances in the brain, much more severe than an occasional case of "the blues." Depression affects the whole body: energy level, appetite and concentration.

"What we're really finding is that people that are depressed are quite inactive, both in kind of expending energy and in getting things done, working toward goals, taking care of personal business," said Matt Kushner, a clinical psychologist and associate professor of psychology at the University of Minnesota.

He recommends exercise for his patients as part of therapy that emphasizes routines, habits and goals. In addition, he said, patients who start exercising find they feel better and are less inclined to overeat or abuse drugs and alcohol.

"If I could pick one activity from a long list ... exercise would always be the one I would go to," he said. "Exercise is sort of a gift that keeps on giving."

Sue Masemer, an exercise physiologist, said there's no definitive research explaining exactly how exercise affects one's mood. But, she said, there's no doubt there's a connection between the physical body and the mental psyche.

"There are those pieces that are almost somewhat intangible," Masemer said. "As (people) get in better shape, they have more energy, accomplish more ... people are amazed at what they are able to accomplish, physically and emotionally."