For women with serious depression, a single session of exercise can change the body and mind in ways that might help to combat depression over time, according to a new study of workouts and moods. Interestingly, though, the beneficial effects of exercise may depend to a surprising extent on whether someone exercises at her own pace or gets coaching from someone else.
Already, a wealth of recent research tells us that exercise buoys moods. Multiple studies show that physically active people are more apt to report being happy than sedentary people and are less likely to experience anxiety or depression. In a few experiments, regular exercise reduced the symptoms of depression as effectively as antidepressant medications.
But science has yet to explain how exercise, a physical activity, alters people’s psychological health. Many exercise scientists speculate that working out causes the release of various proteins and other biochemical substances throughout our bodies. These substances can enter the bloodstream, travel to our brains and most likely jump-start neural processes there that affect how we feel emotionally.
But it has not been clear which of the many substances released during exercise matter most for mental health and which kinds of exercise prompt the greatest gush in those biochemicals.
Those open questions prompted Jacob Meyer, an assistant professor of kinesiology at Iowa State University in Ames, to start considering endocannabinoids and the runner’s high.
As the name indicates, endocannabinoids are self-produced psychoactive substances, similar to the psychoactive compounds in cannabis, or marijuana. Created in many of our body’s tissues all the time, endocannabinoids bind to specialized receptors in our brains and nervous systems and help to increase calm and improve moods, among other effects.
Past studies show that exercise often increases the levels of endocannabinoids in the bloodstream, probably contributing to the so-called runner’s high that leaves some people feeling tranquil and floaty after workouts.
At the same time, problems with the endocannabinoid system are linked with some mental health concerns. People with diagnoses of depression often have relatively low levels of endocannabinoids in their blood, for instance, while mice and rats born with malfunctioning endocannabinoid receptors typically develop a kind of rodent depression.
So, Dr. Meyer thought, might exercise that increases endocannabinoid levels potentially play a role in combating depression? And if so, what kinds of exercise would produce such an increase, and what kinds would not?
To learn more, Dr. Meyer turned to stored blood samples and other records from a relevant earlier experiment. That research, which he had conducted as a doctoral student at the University of Wisconsin, had involved women with major depression completing a number of workouts on stationary bicycles.
Each of the workouts lasted for 20 minutes, but their intensities varied substantially, from light to draining. During most of the sessions, the women were told how intensely to pedal, with their efforts monitored and adjusted so they maintained that level. But during one workout, they could choose the intensity, pedaling as easily or strenuously as they liked.
Before each session, the women gave blood and completed questionnaires about their emotional states. Immediately afterward, they gave blood again and, 10 minutes and 30 minutes later, repeated the questionnaires.
In earlier studies using data from this experiment, Dr. Meyer reported that any exercise, whether its intensity was light or difficult, left the exercisers feeling more cheerful. However, the positive impacts tended to be more substantial when the women followed directions about how intensely to exercise compared to when they set their own pace.
Now, for the new study, recently published online in Medicine & Science in Sports & Exercise, Dr. Meyer set out to see if any changes in the women’s endocannabinoid levels after the different sessions might have played into that dynamic. For the sake of a simple comparison, he focused on one session in which the women had cycled continuously at a moderate pace and another in which they had pedaled at whatever intensity they chose. For most, their you-pick effort was gentle; but for others, it was moderate, and for a few, intense.
And he found notable differences in outcomes. After both workouts, the women reported feeling less depressed and worried. But only when they had followed instructions to pedal moderately did their blood show increases in endocannabinoids. When they had exercised at their preferred pace, even if it was moderate, endocannabinoid levels remained unchanged.
What these results suggest, Dr. Meyer says, is that being coached and supervised leads to different impacts on our bodies and minds than working at our own pace, whatever that pace might be.
Why the prescribed exercise should have increased endocannabinoids, though, while the go-as-you-please workout did not is still mysterious, he says. It may be that our brains recognize when a workout’s intensity is not one we would voluntarily choose and prompt the release of substances that make the effort more tolerable. That idea requires additional research, he says.
This study also did not look at men with depression or the long-term impacts of the exercise, and whether any increases in endocannabinoids reduced depression over time. In the short term, both types of exercise made the women a bit happier.
Over all, the study underscores that our responses to exercise can be complicated, interweaving the physiological and the psychological, Dr. Meyer says, but any exercise is better for mental health than none.
“It might be helpful for people suffering from depression to work with a personal trainer or other fitness professional” who can supervise the sessions, he says.
But in the end, “for improving depressed mood state, exercise of any intensity appears helpful.”
