At the age of 16, Heather Troupe received a diagnosis of chronic severe depression and a prescription for an antidepressant. Eight years and 20 pounds later, she was sleeping poorly, felt a lot of anxiety and had lost her therapist because of insurance complications. Looking to “fix herself,” as Troupe, of Knoxville, Tenn., put it, she began using an elliptical machine every day at the gym, hoping to sweat away what was ailing her.

Today, Troupe, 33, has been medication-free for nine years and credits her daily exercise habits with helping her achieve mental health. “Exercise has been the biggest piece of the puzzle for me,” says Troupe, who is now a fitness instructor. “It’s a place for me to funnel all that extra energy — energy that would otherwise turn into sadness or anxiety.”

Likewise, Erika Howder of Arlington, Va., says exercise pulled her out of the postpartum depression she developed after having her first baby about 14 years ago. She made an appointment with a therapist for help just a few weeks after that birth, but while waiting for the date to arrive, she began to run on a treadmill. “I felt an improvement almost immediately,” she says. “I know I could have tried meds, but most have side effects. Running gave me the antidepressant I needed without any other issues.” She canceled her appointment and never looked back.

Troupe and Howder’s experience has an apparent scientific basis. A new study by researchers at the University of California at Davis Medical Center found that exercise increased the level of the neurotransmitters glutamate and GABA, both of which are depleted in the brains of patients with depression and anxiety. Neurotransmitters are chemical messengers that allow the brain to communicate with the body.

Chemical messengers

Richard Maddock, a professor of psychiatry and behavioral sciences and lead author of the study, said he hopes the findings will encourage more doctors and patients to consider exercise as therapy for these two conditions. “It’s becoming more accepted, but there hasn’t been enough research in this area to make people confident.”

He noted in a statement explaining the study that “major depressive disorder is often characterized by depleted glutamate and GABA, which return to normal when mental health is restored. Our study shows that exercise activates the metabolic pathway that replenishes these neurotransmitters.”

The study examined 38 healthy volunteers who rode stationary bicycles at a vigorous rate — about 85 percent of their maximum heart rate — for up to 20 minutes in three sessions.Using a type of advanced MRI scanning, the researchers measured GABA and glutamate levels in the brain immediately before and after the exercise sessions.

The scans showed significant neurotransmitter increases in parts of the brain that process visual information and help regulate heart rate, emotions and some cognitive functions. The gains trailed off after 30 minutes. For those participants who had exercised three or four times in the week leading up to the study, there was evidence of longer lasting effects.

The researchers did preliminary scans of all the participants that required they do no exercise in the 24 hours before the study began. The scans showed that “those who had exercised in the week prior already had higher levels than those who had been sedentary,” Maddock said. “The inference here, then, is that regular exercise might keep levels higher all the time.”

Maddock pointed out that exercise is one of the most demanding tasks to ask of the brain, which uses a lot of “fuel” when the body is pushed, even more so than for such intellectually pursuits as chess or calculus. “This is about the brain working better, including those parts of the brain that regulate emotions,” he said. “Those patients whose glutamate and GABA are at low levels are at a disadvantage for controlling their emotions.”

The researchers also scanned the brains of a six-person control group whose members did not exercise. In those cases, no change in neurotransmitter levels was seen.

The results seem to correlate with what Howder experienced as she began running regularly: Her depression slowly began to disappear. “As I ran more and the days passed, I felt more like myself, and the feelings lasted longer,” she said.

‘I felt more like myself’

Other recent studies have shown a link between exercise and reduced depression. A 2011 survey of 11 previous studies, for example, found that exercise appeared to be a significant help to those with depression and suggested doctors begin incorporating it into treatment plans.

Some clinicians have begun to do so.

Jennifer Carter, a clinical assistant professor of family medicine and the director of sport psychology at Ohio State University, said she has been pushing exercise therapy since the early 2000s. “I view balanced exercise as an important component in treating anxiety, depression and other mental-health disorders,” she said. “If clients are depressed, I educate them that the two best self-help strategies are exercise and social support. For anxious clients, I teach them how exercise helps reduce worry, panic and other symptoms.”

Carter adds that although “I inform clients about studies showing that exercise can be as effective and longer-lasting than medicine, I’m not anti-medication,” she said. “Psychotherapy, exercise and medication are all tools that can be effective for mental-health disorders.”

Maddock would like to next study 25 individuals with depression. “We studied healthy people [without depression] and now I would like to see the effects on those with depression who already have low levels of the neurotransmitters,” he said. “It may be that not everyone will respond to exercise but that we could identify those who would and then treat them accordingly.”

Maddock said that one of the most exciting implications of his group’s findings involved patients younger than 25. “This is a population that sometimes has more side effects from antidepressants,” he said. “It’s also a group that is generally physically able to participate in exercise programs.”

This was exactly how things played out for Troupe, who, after starting her routine on the elliptical, cleaned up her diet and added strength training.

“I still struggle from time to time,” she admitted, “but I know that there is no quick fix and that even while taking medication, I had some low points. I feel so much more capable than before I began exercising.”