Exercise should be prescribed more often for those suffering from depression and anxiety, according to a new study.

"Exercise has been shown to have tremendous benefits for mental health," says Jasper Smits, director of the Anxiety Research and Treatment Program at Southern Methodist University in Dallas, Texas, US. "The more therapists who are trained in exercise therapy, the better off patients will be."

The traditional treatments of cognitive behavioural therapy and pharmacotherapy don't reach everyone who needs them, said Smits, an associate professor of psychology.

"Exercise can fill the gap for people who can't receive traditional therapies because of cost or lack of access, or who don't want to because of the perceived social stigma associated with these treatments," he said. "Exercise also can supplement traditional treatments, helping patients become more focused and engaged."

Smits and Michael Otto, psychology professor at Boston University, presented their findings to researchers and mental health care providers 6 March at the Anxiety Disorder Association of America's annual conference in Baltimore.

Their workshop was based on their therapist guide Exercise for Mood and Anxiety Disorders, which draws on dozens of population-based studies, clinical studies and meta-analytic reviews that demonstrate the efficacy of exercise programs, including the authors' meta-analysis of exercise interventions for mental health and study on reducing anxiety sensitivity with exercise.

"Individuals who exercise report fewer symptoms of anxiety and depression, and lower levels of stress and anger," Smits said. "Exercise appears to affect, like an antidepressant, particular neurotransmitter systems in the brain, and it helps patients with depression re-establish positive behaviours. For patients with anxiety disorders, exercise reduces their fears of fear and related bodily sensations such as a racing heart and rapid breathing."

After patients have passed a health assessment, Smits said, they should work up to the US public health dose, which is 150 minutes a week of moderate-intensity activity or 75 minutes a week of vigorous-intensity activity.