Considering that DHEA is a steroid... of course they're going to get muscle growth and better sense of well being seeing as how testosterone naturally drops in early to mid 30s for men.
DHEA (dehydroepiandrosterone) is the first one on the left side in purple.
http://en.wikipedia.org/wiki/File:Steroidogenesis.svg
I would not play around with steroids unless you have a legit medical case for androgen replacement through a doc. If you're having problems with low androgens see a doc about it.