There are well-designed, controlled studies that show significant benefit of exercise intervention on both mood and brain functioning. While many of these have studied people who are only mildly or moderately depressed, there are some studies with people who have actually been diagnosed with clinical depression, using strict criteria. Most notable among these is a study by James Blumenthal and colleagues at Duke University of the effects of aerobic exercise, published in the journal Psychosomatic Medicine. Aerobic exercise is exercise that increases heart-rate and improves the flow of oxygen through the lungs. The researchers assigned 156 middle-aged or elderly patients with a diagnosis of major depression to either an exercise condition, an antidepressant medication condition, or a combination of the two. The exercise consisted of 3 weekly 30-minute sessions of either stationary bike-riding or running on a treadmill at 70-85% maximum heart-rate. The intervention lasted for four months, and then participants were reassessed at six months after the end of the intervention. All three groups showed significant decreases in depression, including complete remission for some. Those who exercised on their own at follow-up had a better outcome.
The issue with aerobic exercise is that it's difficult to start a running practice, particularly if you're a busy mom or worker. It often requires getting up at 5 in the morning. Then there are the safety issues if you run outside. We have heard many stories of lone woman joggers on trails being raped. Using a treadmill at a gym is one way to go, if you don't have to take the dog out as well, can afford it, and/or live near the gym. If waking up at 5am to run is difficult for most people, think how much harder it is for depressed people who often can't get out of bed! Luckily for the less motivated among us, aerobic exercise is not the only type of exercise shown to be beneficial for depressed mood. While there is some evidence from a comparative study showing vigorous exercise is more effective than mild exercise, other studies show benefits of yoga, Taekwondo, weight-bearing exercise, and even walking on depression.
Notably, in the yoga studies 60 minutes of yoga 3 times a week improved not only depression, but anxiety, and levels of GABA in the brain. GABA is a chemical associated with stress modulation. Therefore, yoga seemed to change brain functioning to help people manage their stress better. Yogic breathing interventions have also shown efficacy with people whose depression was not remitted completely with medication. Studies by Shapiro and colleagues at UCLA demonstrated this effect and also showed beneficial effects of yoga on the variability of heart rate, an important measure of physiological wellbeing and balance. There is also evidence that physical inactivity seems to interfere with brain neuron regeneration.
So, there seems to be reason to get up off your chair and get moving - easier said than done for a depressed person, but perhaps doable if they start slowly and build up. It would be great if exercise worked as well as antidepressants because it is less costly and has fewer negative side-effects. It may begin to work fairly quickly as well. One study showed some mood benefits after a single exercise session. Unfortunately, if we take a closer look at the research literature, it may be premature to throw out the antidepressants (or psychotherapy sessions) just yet. A group called the Cochrane Collaboration publishes meta-analyses, or overall statistical summaries of the research on effects of different interventions. When looking at the research literature on exercise and depression, they found that many studies were not well-enough designed to meet the criteria. Studies often had small numbers of people participating, too many people dropping out, or did not control enough for expectation of improvement. For example, people may expect to improve more with yoga than listening to a lecture or walking slowly. When they looked at the handful or less of studies that met their strict criteria, they found only a smallish benefit of exercise that was not statistically significant. Another group of researchers from Europe did a similar type of analysis and concluded based on the 5 best studies that there were no long-term benefits of exercise on clinical depression, once expectation was controlled for.
How do we interpret all of this? For most of us out there who get blue sometimes or are mildly to moderately depressed following some stressor, exercise may be a good first step to feeling better. It may have social benefits as well. If you join a running group or attend a yoga class, you may make new friends. On the other hand, for people who are actually clinically depressed, exercise should be used together with psychotherapy or medications, rather than as a substitute for now. And many more studies need to be done that may change these recommendations.....
As I said in the beginning, it's complicated!