Anyone who has practiced yoga for a while knows from their own experience that it offers all kinds of benefits – strength, balance, focus, relaxation, deeper sleep, etc, etc – but here, for those of you who'd like to see some documented evidence, is an article about a study that proves it. (Thanks to TA for the link.)
The study demonstrated that yoga (interestingly, all kinds of yoga) tends to elevate levels of a certain brain chemical called GABA. Low levels of GABA are associated with depression, and PMS moodiness, apparently. The end of the article also cites a study linking yoga to reduced frequency and intensity of migraine headaches.
The key is just regular, moderate practice. Sometimes people tell me that they know yoga would be good for them, but that they didn't really like it when they tried it. If that's you, I encourage you to shop around for a different teacher, studio, or style. There's such an enormous diversity these days that you really can't judge all yoga by your experience in one setting.
Of course, also feel free to listen to your own wisdom about what is right for you! If it's not yoga, then maybe it's Tai Chi, Aikido, Nia... or something else altogether. You're the boss... but do yourself a favour and try something for your body that's well away from your desk chair. :)
I want better studies
But what I think a better headline would have been is "Yoga releases more of this brain chemical than sitting around reading", which isn't real surprising. (And a better summary here, "Yoga better for mental state than sitting and reading". On the other hand an hour of Yoga won't get you through any reading...)
I'd like to know if an hour of any light activity has the same effects (like you say, pretty much). I wouldn't be at all surprised if it did - heck, I'm sure it doesn't have to be even vaguely "Eastern" to do it.
(I don't do yoga, but the benefits specific to it compared to any other light activity, I'd expect to be in flexibility and the like. Stretching does that.)
(PS. Might want someone to look at the comment/preview functionality. Nobody should have to add Break tags to get paragraphs!)