Does physical exercise aid mental health?
A new study has questioned whether the mental perks of exercise are the result of the placebo effect.
Science tells us that exercise can make us smarter.
Research has even shown that endurance exercise elevates levels of a molecule known to protect the brain's health and activates genes associated with learning and memory.
Separate to this, a fit body promotes a mentally fit mind.
"Chronic stress, anxiety, and depression have been linked to atrophy or loss of neurons, and exercise has been linked to the growth of new neurons," writes Christopher Bergland in The Athlete's Way. "The primary hormone triggered during the degeneration of neurons seems to be cortisol, which appears to shrink the hippocampus, our memory hub."
But, a new study has questioned whether the mental perks of exercise are the result of the placebo effect.
The placebo effect is the phenomenon of people's health improving, from a "pretend" treatment, simply because they expect it will. As much as one third of people who take a placebo report improvements.
For instance, a study from earlier this year, found that when migraine patients were given a placebo or a migraine drug with the labels switched, the severity of their self-measured pain improved to a similar degree. The researchers concluded that the placebo effect accounted for more than 50 per cent of the drug's effect.
The placebo effect is typically discussed in relation to pills or drugs, but also encompasses other "treatments" including diet and exercise.
"A number of studies and meta-analyses conclude that aerobic fitness (walking) interventions improve cognition," said the study's authors from Florida State University.
However, "if participants expect greater improvement following aerobic exercise, then the benefits of such interventions might be due in part to a placebo effect."
So if participants in past studies expected certain cognitive improvements, then they tended to perform better in those areas in subsequent tests. And this, the Florida State scientists suggested, may have been largely the result of the placebo effect rather than long-lasting changes to the brain.
They were unsure whether this was the case, however, because previous studies have not used placebos.
So the researchers recruited 171 volunteers, divided the group into two, and asked them to estimate how much exercising three times a week might improve their memory and mental multitasking.
The first group were asked about stretching and toning (which, unlike walking, has not been shown to have a cognitive impact) while the second were asked about walking as their form of exercise.
The participants however believed the opposite, with the stretching and toning group anticipating that their mental gains would be greater than those of the walking group.
It is an unusual study of exercise in that it did not actually involve any exercise, but the authors argue it shows that expectation does not appear be driving the results in previous studies.
"If people have roughly comparable expectations for improvement or if their expectations favour the stretching and toning condition, then placebo effects are unlikely to drive the cognitive gains from aerobic exercise," they said in the paper published in the journal Plos One.
The benefits, therefore, might be in our minds, but the improvements are real and for a ship shape mind and body, exercise is still a highly effective treatment.