A few years ago, as part of an article I wrote, I suggested that exercise is very helpful for depression, purely based on my own experience. Back then I didn’t have any studies to back up my assertion. Now I do: a recent study by researchers at the University of Texas at Austin found that 30 minutes of brisk walking can temporarily lift the mood of people with depression.

The participants in the study were divided into two groups. During a 30 minute period, one group sat quietly and the other...