Scientists are sticklers for not really believing what until someone explains how. That is, they’ll see that something happens, but until research reveals how it happens the phenomenon remains a bit dodgy.
So it is with the power of exercise to spur the production of new neurons in the brain, improve learning and lift depression. Fred Gage and colleagues at the Salk Institute showed in 2005 that it does happen—even elderly rats have a spurt of this “neurogenesis” after a few sessions in the exercise wheel. And researchers led by Arthur Kramer at the University of Illinois showed in 2006 that the effect occurs in people, too, so that even a hour a day of mall-walking increases the amount of gray matter in the brains of the elderly. It also makes you feel better.
Maybe now more scientists, not to mention the rest of us, will take the findings to heart. Researchers led by Ronald Duman of Yale have discovered that exercise causes the brains of mice to produce a molecule that acts as a natural antidepressant, they write this afternoon in the online edition of Nature Medicine. The molecule is a growth factor called VGF, which is active in the brain.
That nearly ties up three loose ends: exercise, neurogenesis and anti-depressants. That's because, over the last few years, scientists have been challenging the idea that antidepressants such as Prozac work by increasing the brain’s production of serotonin. Instead, the drugs' real mechanism is to spur neurogenesis. With the new work, there’s at least the possibility that the drugs do so through VGF. The current study shows that “VGF is required for the antidepressant effects of exercise,” the scientists say. Interesting, the most effective treatment for depression, electroconvulsive shock, also increases the brain’s supply of many of the molecules that exercise does, including VGF.
The next step is to confirm that exercise also raises levels of VGF in people's brains, not just mice's. But as anyone who has experienced a glow or even a euphoria from working out can attest, exercise has a profound positive effect on mood--and now we know how.