From an article in the August/Septermber 2008 Scientific American "Depressingly Easy," by Kelly Lambert

FAST FACTS
The Mental Perils of Ease
1>> Rates of depression have risen in recent decades, at the same time that people are enjoying time-saving conveniences such as microwave ovens, e-mail, prepared meals, and machines for washing clothes and mowing lawns.
2>> People of earlier generations, whose lives were characterized by greater efforts just to survive, paradoxically, were mentally healthier. Human ancestors also evolved in conditions where hard physical work was necessary to thrive.
3>> By denying our brains the rewards that come from anticipating and executing complex tasks with our hands, we undercut our mental well-being.