Interesting article that you might find interesting....

Interesting article- the theory of how friends and people around you not only affect one another but also those who are 3 degrees away as well. Read the first 3 pages at least. Involves smoking, health, cheer, grief, obesity, fitness, etc.
NEW YORK TIMES

Some of the tests done are really speculative, however, while reading I myself noticed similar behavior patterns and social effects among people in my own circles of concern and general region.
Let's not forget that there are emotional and spiritual ties among one another. This also tunes into the effects of social behavior and affects the outcome of day to day living as well as long term adjustments that may be made, coincidental, or based on actual ties that bind.