The Rat Park studies strongly suggest that this is true. Rats studied in conditions where they have every reason to be happy did not suffer from drug addiction, even when drugs were made available to them. Rats kept in cages isolated from each other (rats are very social creatures) became seriously addicted.

https://en.wikipedia.org/wiki/Rat_Park

http://www.brucekalexander.com/articles-speeches/rat-park/14...

http://www.stuartmcmillen.com/comics_en/rat-park/