Here's a teaser:
Americans put far too much emphasis on finding Mr. or Ms. Right and getting married. We think this will bring us happiness. In fact, however, both psychological well-being and health are more strongly related to friendship. If you have good friends, you’ll be less likely to get the common cold, less likely to die from cancer, recover better from the loss of a spouse, and keep your mental acuity as you age. You’ll also feel more capable of facing life’s challenges, be less likely to feed depressed or commit suicide, and be happier in old age. Having happy friends increases your chance of being happy as much as an extra $145,500 a year does. So, make friends!
Here is the whole article.