New findings highlight strong link between exercise and depression

When wildfire smoke descended on British Columbia in the fall of 2020, people responded to the polluted air by exercising less. They also felt more anxious, stressed, and depressed – and those two observations are connected, according to new research from the University of the Fraser Valley.

The links between physical activity and mental health are well-known in scientific circles. Earlier this year, a major review of more than 200 studies confirmed that exercise is an effective treatment for depression. Canadian guidelines in place since 2016 recommend exercise as a first-line depression treatment, with effects comparable to psychotherapy or medication.

But there’s often a gap between theory and practice. The new study on wildfire smoke, which was led by Fraser Valley kinesiology professor Luisa Giles and appears in the Journal of Physical Activity and Health, offers a “natural experiment” that reveals what happens when people are forced to cut back on their usual physical activity.

Giles and her colleagues asked volunteers to fill out questionnaires on their exercise levels and mental health, during both smoky and non-smoky periods. On average, the respondents got 20 to 30 minutes less moderate or vigorous exercise on smoky days; they also reported higher levels of stress, anxiety, and depression. Crucially, the bigger the drop in an individual’s physical activity levels, the more likely they were to suffer a drop in mental health.

Two key points connect the wildfire findings to broader discussions about exercise and mental health.

The first is that people whose psychological profiles showed higher levels of autonomy, self-determination, and intrinsic motivation were more likely to find ways of continuing to exercise on smoky days. But these are also the traits that depression undermines, creating a vicious cycle: depression makes you less likely to exercise, which in turn exacerbates depression.

Climate change is a growing threat to our love of sports. But can we adapt?

The second is that only 10per cent of Giles’s respondents discussed the problem of exercising in polluted air with their doctor. Given the current realities of primary care access in Canada, the same barrier limits the deployment of exercise as a tool to fight depression. The evidence may be strong, but most doctors have neither the time nor the expertise to start prescribing and monitoring workouts.

To address that gap, the Canadian Society for Exercise Physiology announced last month that they’re launching a new certification for personal trainers and exercise physiologists who complete 40 hours of specialized training plus an exam on exercise and depression.

The program was developed in collaboration with researchers at the University of British Columbia, led by Guy Faulkner, a professor of applied public health. The researchers have run pilot programs targeted at students on campus suffering from depression as well as for women in the community, combining exercise classes with additional support on behaviour change strategies.

The student-focused Mind in Motion program, for example, involved two weekly hour-long sessions in small groups, led by a personal trainer, with a mix of cardio and strength exercises. After six weeks, average scores on a standard depression questionnaire had dropped from 10.6, corresponding to moderate depression, down to 5.3, on the border between minimal and mild depression.

Scientists are still debating exactly how exercise combats depression – whether it’s elevated levels of mood-altering brain chemicals like serotonin, the growth of new brain cells, or even the sense of accomplishment that accompanies a successful workout. Whatever the mechanism, it’s increasingly clear that it works.

That leaves the practical questions. How do you maintain your fitness regimen in the face of disruptions like wildfire smoke? Giles suggests N95 masks for those determined to exercise outdoors, and community initiatives like free access to recreation centres with indoor workout facilities on bad-air days.

And how do you get started on an exercise routine if you’re already struggling with depression and its accompanying motivational challenges? There’s no simple answer, but if CSEP’s new exercise and depression initiative takes off, a prescription for personal training might be a good start.

Alex Hutchinson is the author of the forthcoming book The Explorer’s Gene: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map.