Serious discussions of happiness were once the business of philosphers. But social scientists and neural scientists are now in the game because they have each developed powerful new tools.
The Spring 2008 Journal of Economic Perspectives includes Angus Deaton's "Income, Health and Well-Being around the World: Evidence from the Gallup World Poll". It turns out (surprise) that the links are not simple.
Nevertheless, as more and more people are living lives beyond the Malthusian trap, there good grounds for the positive view. If recognizable humans have been around for 50,000 years and if the escape from Malthus is only in the last 250 years, we are talking about the only last one-half of one percent of our existence.