You’re the average of the 5 people you spend the most time with’ – Jim Rohn
Your circle of influence does not fall short here, it has a social network affect extending up to three degrees of separation (for example, to the friends of one’s friends’ friends).
Christakis and Fowler evaluated a densely interconnected social network of 12,067 people assessed repeatedly from 1971 to 2003 as part of the Framingham Heart Study.
The risk of obesity to individuals who were connected to:
- A friend who is obese (at one degree of separation) equates to a 45% higher than normal chance to develop obesity
- 20% higher from a friends’ friend (at two degrees of separation)
- 10% higher for friends’ friends’ friend (at three degrees of separation) 
These stats may be daunting however we can reap positive benefits from this cascade of influence. It’s common knowledge that friends make us happier:
- A friend who lives within a mile radius and becomes happy increases the probability that the individual is happy by 25%
- Similar effects are seen in co-resident spouses (8%)
- Siblings who live within a mile (14%)
- Next door neighbours (34%) 
Our environment subliminally installs lenses of perception which distorts our internal interpretative software. Thus altering expectations, social framework and values whilst we blindly adopt this as the cultural norm.
We may have even heard of the quote,
“Show me your friends and I will show you your future”.
This is a biblical concept as in Proverbs 13:20, Solomon, wrote:
“He that walketh with wise men shall be wise: but a companion of fools shall be destroyed”.
Selectively auditing associates is essential in self-preservation.
If your circle doesn’t have individuals who inspire, support, or elevate you … you don’t have a circle, but a cage.
As for smoking , there is a direct influence on the likelihood of smoking yourself with a:
- 61% increased likelihood if your friend smokes
- 29% increased likelihood if a friend of a friend smokes
- 11% increased likelihood if a friend, of a friend, of a friend smokes
Ambivalent relationships, individuals languishing in the grey-zone of confusion due to holding undecided mixed-views about the quality of your friendship, have been labeled as detrimental as toxic relationships. Attributes contributing to this category commonly fit that of jealousy, uncertainty, and undermining demeanours. These clouded friendships increase the likelihood of illness, decreased job satisfaction, and higher stress 
- N Engl J Med 2007; 357:370-379
- BMJ 2008;337:a2338
- N Engl J Med 2008; 358:2249-2258
- Gerontol B Psychol Sci Soc Sci. 2008 November ; 63(6): P362–P371.