Physical activity may be an underused therapy for depression

Doctors should be clearer about prescribing exercise, psychiatrists say, because physical activity may help with depression, memory, and overall mental health.

A five-minute walk can seem simple until depression drains a person’s energy. At that point, advice to exercise more can leave someone unsure how to start.

Research suggests that exercise can reduce depression symptoms.

Three Canadian psychiatrists argue that exercise should be prescribed with the same care given to antidepressant drugs.

Carl Zhou and Nicholas Fabiano are based in the psychiatry department at the University of Ottawa, while Stanley Wong works in the psychiatry department at the University of Toronto.

Their commentary relies on earlier studies and does not present new experimental results.

“We still tend to treat exercise as general lifestyle advice,” Zhou said.

“The evidence we reviewed supports something more deliberate: a prescription that names the type of activity, the frequency, the intensity, the duration, the safety considerations, and a plan for follow-up, just as we would for a medication.”

Signals from muscles

When a muscle contracts, it does more than move a limb. It also releases molecules known as myokines, which may interact with chemical pathways linked to mood and cognition.

Researchers refer to this proposed link as the muscle-brain axis. The authors present it as one possible explanation for exercise’s effects, while allowing for other mechanisms as well.

The brain depends on good blood flow, healthy metabolism, and control of inflammation. Learning also requires the brain to reshape the connections between its cells.

Exercise affects the heart, blood vessels, immune system, and growth signals that support learning.

Improved sleep, greater confidence and social contact, and reduced risk of vascular and metabolic disease may also help explain its benefits.

One year of training

Kirk Erickson’s team followed 120 older adults without dementia for a year to study exercise and brain health.

In that trial, one group did moderate aerobic exercise and the other did stretching.

The researchers focused on the hippocampus, a brain region important for memory.

The hippocampus grew by about two percent in the aerobic group, mainly at the front, but shrank in the stretching group.

The team said the increase was equivalent to reversing one to two years of age-related shrinkage.

Among the people who exercised, more growth was associated with greater improvement on a memory test.

Physical activity has also been tied to better thinking skills and lower risk of dementia and Alzheimer’s disease.

Those findings mostly come from observational studies, which cannot prove that exercise itself caused the difference.

Exercise tested for depression

Researchers have evaluated exercise for depression and anxiety in randomized trials, where chance determines who receives each intervention.

The results indicate that activity programs can reduce symptoms.

Walking, jogging, yoga, and strength training have all shown benefits.

A review published in The BMJ pooled 218 trials involving 14,170 people with depression and reached a similar conclusion.

More vigorous exercise generally appeared to bring greater relief, but the evidence has limits.

Only one trial met the reviewers’ strictest standard for avoiding bias, and their confidence in the overall findings was low or very low.

Even a little helps

For people who struggle to exercise, another finding may be especially encouraging.

A 2022 analysis of 15 long-term studies involving 191,130 adults found a lower risk of depression even when people did less than the recommended amount of activity.

Those who did about half the recommended level had an 18% lower risk than people who reported no activity. Those who met the full recommendation had a 25% lower risk.

Because these were observational studies, the numbers do not prove cause and effect. The biggest difference was between doing nothing and doing some activity.

For patients who cannot yet meet the full target, the authors suggest starting with about 75 minutes of moderate activity a week.

That is roughly half the usual minimum recommendation.

Thinking skills and schizophrenia

Drugs for schizophrenia offer only limited help with thinking problems, even though those problems affect daily functioning. Exercise may help fill that gap.

A 2017 analysis of ten trials involving 385 people with schizophrenia found improved overall cognition with aerobic exercise.

Exercise also appeared to help working memory, which supports holding and using information, and social cognition, which helps people interpret others’ behavior.

People with schizophrenia and other severe mental illnesses often spend long periods sitting and have high rates of heart disease, metabolic disease, and early death.

The authors point to the illness itself, social disadvantage, and the metabolic side effects of some medicines.

“In schizophrenia, exercise can work on psychiatric symptoms, cognition, and physical health at the same time, in a population with substantial unmet needs in all three,” Wong said.

Still, the cognitive findings come from only a few small studies.

How to begin

The World Health Organization recommends 150 to 300 minutes of moderate activity each week for adults, along with muscle-strengthening exercise on at least two days.

Brisk walking counts as moderate activity, while running or fast cycling falls into the vigorous range of 75 to 150 minutes per week.

Patients do not need to begin at that level.

If depression has reduced energy, motivation, and concentration, the first step may be a five-minute walk, a walk with the dog, or seated exercises.

“The starting point does not have to be impressive,” Fabiano said. “It has to be possible.”

For most patients, the authors recommend a low-risk activity that can be increased gradually.

Pain or dizziness may mean the plan should be adjusted, while chest pain or severe shortness of breath requires immediate medical attention.

Some people may need medical evaluation, physiotherapy, supervision, or a short pause before increasing activity.

That includes people who are frail or who have unstable heart or breathing symptoms, recent falls or fainting, infection, or uncontrolled pain.

Support beyond the prescription

Wong wants larger trials to determine whether the cognitive gains seen in schizophrenia can be confirmed. The current studies do not settle the question.

Researchers are also studying exercise mimetics, which are drugs or other agents that may reproduce some of the chemical effects of exercise.

In theory, these could help people with depression when symptoms, disability, or frailty make movement difficult.

The authors view such approaches as possible additions to care, with safe activity continued whenever it is feasible.

They also warn that exercise prescriptions could widen health inequities if patients do not get the help they need to carry them out.

They call for publicly funded community exercise programs, transportation support, and partnerships with recreation and community centers.

The aim is not to make every patient an athlete, but to make physical activity a practical and supported part of mental health treatment.

The opinion piece appears in the journal Brain Health.