This was an unexpected finding. There is no obvious explanation.

What the studies are showing is that exercise, at least when performed in a group setting, seems to be at least as effective as standard antidepressant medications in reducing symptoms in patients with major depression,

But we also know that these drugs aren't effective for everyone -- about a third of people aren't going to get better with medication.

Social support, peer pressure, family support -- all of that can be helpful, certainly in getting people to maintain exercise.

duration of exercise didn't seem to matter -- what seemed to matter most was whether people were exercising or not.

[From a data standpoint,] it's a relatively slow week but what little there is probably not going to be that friendly, ... It's not going to change the market's perception of the Fed, and Greenspan is unlikely to change the market's perception either.