There are studies that show a strong correlation between meditation and higher levels of happiness and lower levels of stress. These studies are a big part of why meditation is sort of trendy nowadays AFAIK. Googling [meditation study stress] (or whichever claim you're interested in) will yield a number of relevant results.

There seems to be quite a lot of research on this topic, see http://en.wikipedia.org/wiki/Research_on_meditation

This article: "Mindfulness-based stress reduction and health benefits. A meta-analysis" http://www.ncbi.nlm.nih.gov/pubmed/15256293 seems to be relevant to your question.

Of course the mere existence of articles does not prove anything. Caution advised :)