Maybe, despite the complex biological links between heart and mind, it all comes down to lifestyle.
"We think exercise is a critical factor in modulating the outcome," says Duke University chief of psychiatry K. Rama Ranga Krishnan. "It works directly and indirectly on a number of factors common to depression and heart disease. It helps depression and it helps cardiac disease." And it does so at many points in paths of both conditions. Adds Emory cardiologist Viola Vaccarino: "Exercise and omega-3 fatty acids are recommended for everyone. But they may be especially critical for those with depression."
- Animal studies show that exercise directly alters levels of neurohormones such as norepinephrine in the brain's frontal cortex and in the hippocampus. Both are brain regions involved in circuits of emotion.
- Exercise appears to stimulate the vagus nerve, the major channel of the parasympathetic half of the autonomic nervous system. It stabilizes heart function and counterbalances the sympathetic hyperactivity identified in depression. It also improves function of the brain's emotion-sensing network.
- By acting on neurohormones that govern the stress response, exercise improves the ability of the body to tolerate stress.
- Exercise stimulates production and expression of the nerve growth factor BDNF (brain-derived neurotrophic factor). This protein, elaborated in brain cells, may be the final common pathway by which all antidepressant therapies work. BDNF helps rewire the brain; it induces brain cells to reinforce old connections and to forge new ones, restoring memory and cognitive flexibility to the depressed.
- Exercise directly reverses insulin resistance, restoring the body's sensitivity to this important hormone.
- Exercise directly burns energy, promoting weight loss.
- Studies show that low-intensity exercise boosts immunity and reduces levels of the inflammatory marker C-reactive protein—even in people genetically predisposed to develop cardiovascular disease.
- Over the long term, exercise also stimulates the growth of new blood vessels, so-called collateral circulation, boosting the general function of both brain and heart by maximizing delivery of oxygen.
- Raising heart rate by exercise delivers more blood to the brain, feeding it nutrients and oxygen that boost mental functions.
- Exercise elevates mood by psychological means as well as physiological ones. It changes people's perception of themselves, providing a sense of personal mastery. It also reduces negative thinking.
If there's one person associated with the role of exercise in depression it's James Blumenthal, Ph.D., professor of medical psychology at Duke University. He was one of the first to test aerobic exercise in people with moderate to severe depression. The patients, sedentary men and women over age 50, worked out for 30 minutes three times a week in groups. Their response was compared with that of similarly depressed patients who received either standard therapy with Zoloft or drug and exercise combined.