system
Given the following post, respond as if you're commenting on Reddit:
human
Sociology says people with friends who are friends among themselves are happier. Is there any science on what's the most effective way to create or enlarge an interconnected group of friends?

Christakis and Fowler argue in their book "Connected" that people who have friends who are also friends among themselves tend to be happier.

I was wondering if there's any science on what's the most effective way to create and enlarge such tightly knit networks. For instance, what's the best way to make the group interconnected? You just put everybody in a room and facilitate conversation? Or you start out with a small group and enlarge it as you go on? In which case what's the best way to introduce new friends to your already well-connected group of friends? You introduce new ones one at a time?

This kind of things...
gpt
Have you tried looking into studies regarding the psychological/social benefits of team sports/activities? 

I believe the "unified goal" aspect of team sports/activities could facilitate the quality of "interconnectedness" you're seeking to foster.

Also, you probably want to clarify how (if at all) Christakis and Fowler talked about these interconnected friend groups numerically (e.g. - is there an optimal amount of interconnected friends, and at what point does the benefit of adding people to the interconnected group plateau and/or start to diminish?).