Working
off depression
(This article was first printed in the December
2005 issue of the Harvard Mental Health
Letter. For more information or to order,
please go to http://www.health.harvard.edu/mental.)
A good workout makes you feel better, and regular
exercise not only enhances physical health but
can lift mood, reduce stress, and heighten self-esteem
by improving appearance and physical strength.
But how useful is exercise for people with severe
depression or anxiety or chronic mental illness?
Hundreds of studies now show that it can help — but
there are qualifications.
Many reviews and meta-analyses show that regular
physical activity is correlated with improvement
in clinical depression and anxiety, mild to moderate
depressive symptoms, insomnia, and resilience
under stress. People who become or remain physically
fit or active are less likely to develop clinical
depression.
For example, in a study published in 2005, researchers
examined the effect of a three-month exercise
program on mild to moderate depression. About
80 participants were divided into five groups.
Two groups took on a rigorous “public health
dose” program, one of them for three days
a week and the other for five days a week. Two
groups instead participated in lighter “low-dose” exercise
three or five days a week. A fifth group, the
controls, practiced only stretching for flexibility.
Ratings of depressive symptoms on the standard
Hamilton scale fell in all five groups, but the
rigorous exercise program caused the biggest
drop, an average of 47%. That made it about as
effective as antidepressant medications or cognitive
behavioral therapy, standard treatments for depression.
The low-dose exercisers did no better than the
controls, but even patients in these three groups
showed some improvement. Any physical activity
may have helped.
Exercise has also been found equivalent to cognitive
behavioral therapy and antidepressants in direct
comparisons. One study compared aerobic exercise
with antidepressant drugs or a combination of
the two in patients with major depression. After
16 weeks, 60%–70% in all three groups had
recovered from the depressive episode, but the
exercise effects may have lasted longer. Ten
months later, patients in that program had a
lower rate of depression than those who took
only medication. In other studies, exercise programs
have equaled the effect of cognitive behavioral
therapy on depression and anxiety.
In a study of more than 2,000 elderly people,
daily walking predicted improvement in depressive
symptoms over a three-year period. A comparison
of aerobic exercise alone, exercise with stress
management training, and routine medical care
for patients with heart disease found that after
16 weeks, patients in both exercise groups had
lower rates of depression. Similar results have
been found for anxiety disorders — panic
disorder, generalized anxiety, and post-traumatic
stress.
Exercise is well known to improve sleep, partly
because depression and anxiety are major causes
of insomnia. For example, one study found that
16 weeks of moderate exercise helped a group
of middle-aged insomniacs to fall asleep an average
of 15 minutes sooner and sleep 45 minutes longer.
How it works
It’s obvious that poor physical fitness
can lead to ill health, and ill health to depression
and anxiety. If physical condition and depressive
symptoms are mutually reinforcing, treating one
can improve the other. But that is apparently
not how exercise works in most cases. In a review
of 30 trials, it made little difference how much
a person exercised, how intensely, or how long.
What mattered was only how long the program lasted — at
least two months. Besides, in most studies, improvement
in depression and anxiety is not correlated with
increased strength or cardiovascular health.
And aerobic exercise and strength training are
usually found to be equally effective.
Other possible explanations for the mood enhancing
effect of exercise include enhanced body image,
social support from exercise groups, and distraction
from everyday worries. Meeting the challenge
of continuing exercise may heighten self-confidence.
Physical activity may affect mood by altering
the circulation of the neurotransmitters serotonin,
norepinephrine, and the endorphins.
Another theory starts with the observation that
for most people, not only those who are depressed
or anxious, an exercise routine is difficult
to start and even more difficult to keep up.
It’s possible that exercise is a form of
controlled, predictable stress that supplies
a kind of vaccination against the uncontrolled
stress that leads to depression and anxiety.
Problems
It’s also possible that this effect of
exercise is an illusion. According to some surveys
and purely observational studies, it could be
that depression and anxiety prevent people from
exercising rather than the other way around.
Or some feature of personality or upbringing
might cause both depression and sedentary habits.
In some studies, the patients least likely to
relapse are those who continue to exercise when
they are no longer participating in a formal
program. So ability to exercise might be evidence
that the depression or anxiety has improved rather
than a cause of the improvement.
Even controlled trials often present problems — especially
insufficient follow-up, the difficulty of correcting
for the effect of expectations, and the fact
that people who volunteer for exercise studies
are not necessarily typical. Many other factors
may be incidentally associated with exercise,
too — the chance to master a skill, associate
with a group of like-minded people, or just do
something interesting and engaging.
These doubts may not matter, because exercise
does so little harm (apart from injury, there
is the rare risk of exercise addiction, mainly
in people suffering from anorexia nervosa). But
low motivation is a problem. We are often told
to find an activity we enjoy, but depressed people
don’t enjoy anything much. So it’s
necessary to begin slowly and remind them that
exercise does not have to be strenuous to be
helpful. Walking, gardening, or household work
will do. Some will want to exercise by themselves;
others may prefer to join a friend or group for
encouragement and mutual aid.
Exercise will not have the same effect on everyone,
and by itself, in most cases, is not an answer
to problems of mental illness. But it costs little
or nothing, rarely has harmful side effects,
and almost always promotes physical health. Although
it is no magic remedy, there is little to lose
and everything to gain by trying to work off
depression and anxiety.
(This article was first printed in the December
2005 issue of the Harvard Mental Health
Letter. For more information or to order,
please go to http://www.health.harvard.edu/mental.)
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