How Exercise Might Keep Depression at Bay (1)

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How Exercise Might Keep Depression at 
Bay 
 
 
Exercise may be an effective treatment for depression and might even help 
prevent us from becoming depressed in the first place, according to three timely 
new studies. The studies pool outcomes from past research involving more than 
a million men and women and, taken together, strongly suggest that regular 
exercise alters our bodies and brains in ways that make us resistant to despair. 
Scientists have long questioned whether and how physical activity affects mental 
health. While we know that exercise alters the body, how physical activity affects 
moods and emotions is less well understood. 
Past studies have sometimes muddied rather than clarified the body and mind 
connections. Some randomized controlled trials have found that exercise 
programs, often involving walking, ease symptoms in people with major 
depression. 
But many of these studies have been relatively small in scale or had other 
scientific deficiencies. A major 2013 review of studies related to exercise and 
depression concluded that, based on the evidence then available, it was 
impossible to say whether exercise improved the condition. Other past reviews 
similarly have questioned whether the evidence was strong enough to say that 
exercise could stave off depression. 
A group of global public-health researchers, however, suspected that newer 
studies and a more rigorous review of the statistical evidence might bolster the 
case for exercise as a treatment of and block against depression. 
So for the new analyses, they first gathered all of the most recent and best-
designed studies about depression and exercise. 
Then, for perhaps the most innovative of the new studies, which was published 
last month in Preventive Medicine, they focused on whether exercise could help 
to prevent someone from developing depression. 
The scientists knew that many past studies of that topic had relied on people 
providing reports about how much they had exercised. We human beings tend to 
be notoriously unreliable in our memories of past workouts, though. 
So the researchers decided to use only past studies that had objectively measured 
participants’ aerobic fitness, which will rise or fall depending on whether and how 
much someone exercises. Participants’ mental health also had to have been 
determined with standard testing at the start and finish of the studies, and the 
follow-up time needed to have been at least a year and preferably longer. 
Ultimately, the researchers found several large-scale past studies that met their 
criteria. Together, they contained data on more than 1,140,000 adult men and 
women. 
Among these million-plus people, the links between fitness and mental health 
turned out to be considerable. When the researchers divided the group into 
thirds, based on how aerobically fit they were, those men and women with the 
lowest fitness were about 75 percent more likely to have been given diagnoses of 
depression than the people with the greatest fitness. The men and women in the 
middle third were almost 25 percent more likely to develop depression than those 
who were the most fit. 
In a separate study (some of the scientists were involved in each of the reviews), 
researchers looked at whether exercise might be useful as a treatment for 
depression. In that analysis, which was published in June in the Journal of 
Psychiatric Research, they pooled data from 25 past studies in which people with 
clinically diagnosed depression began some type of exercise program. Each study 
had to include a control group that did not exercise and be otherwise 
methodologically sophisticated. 
The pooled results persuasively showed that exercise, especially if it is moderately 
strenuous, such as brisk walking or jogging, and supervised, so that people 
complete the entire program, has a “large and significant effect” against 
depression, the authors wrote. People’s mental health tended to demonstrably 
improve if they were physically active. 
The final review offers some hints about why. Published in February in 
Neuroscience and Biobehavioral Reviews, it took on the difficult issue of what 
happens within our bodies during and after exercise that might affect and 
improve our moods. The researchers analyzed 20 past studies in which scientists 
had obtained blood samples from people with major depression before and after 
they had exercised. The samples on the whole indicated that exercise significantly 
reduced various markers of inflammation and increased levels of a number of 
different hormones and other biochemicals that are thought to contribute to 
brain health. 
But the researchers also caution that most of the physiological studies they 
reviewed were too small and short-term to allow for firm conclusions about how 
exercise might change the brain to help fight off gloom. 
Still, the three reviews together make a sturdy case for exercise as a means to 
bolster mental as well as physical health, said Felipe Barreto Schuch, an exercise 
scientist at the Centro Universitário La Salle in Canoas, Brazil, who, with Brendon 
Stubbs, a professor at King’s College in London, was a primary author on all of 
the reviews. 
Many more experiments are still needed to determine the ideal amounts and 
types of exercise that might help both to prevent and treat depression, Dr. Schuch 
said. 
But he encouraged anyone feeling overwhelmed by recent events, or just by life, 
to go for a run or a bike ride. “The main message” of his and his colleagues’ 
reviews, he said, “is that people need to be active to improve their mental health.” 
 
	How Exercise Might Keep Depression at Bay