Depressed patients who are not motivated are not motivated, says Rethorst, so it can be difficult to engage in a new and challenging activity.
Mental health professionals will probably mention exercise along with other healthy tasks such as sleep, to their patients, even though they prescribe talk therapy or medication as the main treatments. But it is not clear how many psychologists or psychiatrists actually prescribe exercise as a treatment.
Some practitioners advocate exercise.
Antonia Baum, a private practice psychiatrist in Bethesda, Maryland, says: "I always take an exercise history with my patients." As for starting and staying in a training program, she speaks through the basics and helps people find an activity that they will enjoy.
"You need to find a way that is sustainable," she says.
A 2015 study suggested that a majority of depressed patients would be interested in trying "a training program designed to improve mood."
Rethorst reviewed the studies to provide guidance for providers on how to prescribe exercise, including what types of exercise, frequency, intensity, duration and how to help people stick to a program.
How Much Exercise? The research studies suggest that at least 150 minutes of aerobic activity – walking, jogging or cycling – a week is good. It is convenient that it complies with the Public Health Guidelines of the Centers for Disease Control and Prevention.
A few studies have found positive effects with resistance training or weight-based training, but there are several signs of aerobic activity.
For people who might want to try exercise as a treatment for low mood or depression, Rethorst says it is still wise to seek a practice help.
"The optimal clinical practice will include regular monitoring of symptoms, as with the initiation of a treatment plan," he says. Worsening of symptoms can lead to different or additional treatments.
In other words, do not exercise yourself as a treatment. If you are really depressed, you need treatment and supervision. For example, exercise does not always work. You may be in danger of not having other treatments ready if you do not see a provider of some sort.
Maintaining a training program is not easy – it is time consuming and it is common to lose motivation at some point. Getting social support by joining a group or class of some kind can help. Baum says she sees her patients regularly enough, often every week, that she can check in and encourage people to stick to it.
Blumenthal says he sees good support for exercising the participants in his studies. But he adds, "We are doing lots of surveillance. The control aspect can be critical."
You may need patience. "The benefits come within six to eight weeks – not immediately," says Blumenthal. "Meds work a little faster."
And of course, exercise is good for many other aspects of your health. "I believe in exercise personally and in my practice," says Baum. "I endorse his beneficial efforts."