A Harvard team was able to demonstrate that when the happiness of your friend increases, it can directly increase your happiness, and in turn improve your overall health. Not only that, but people you don’t even know that are indirectly associated with you via other people can also affect your state of happiness. This BBC link has an audio interview with the lead author.
A recent study with chronic headaches found that those using acupuncture reported improvement in 65% of patients vs. 40% of those who were taking aspirin.
A meta-analysis of over 170 studies publised since 1980 found strong correlations between increased media exposure through television and video games, and obesity, early sexual activity, teen pregnancy, drug use, smoking, and poor academic performance.