There's a famous series of studies from the 1970s about this. Basically, rats stuck alone in metal cages with access to unlimited morphine will consume a hell

There's a famous series of studies from the 1970s about this. Basically, rats stuck alone in metal cages with access to unlimited morphine will consume a hell of a lot more drugs than those in "Rat Parks" with other rats and things to play with. https://en.wikipedia.org/wiki/Rat_Park https://en.wikipedia.org/wiki/Rat_Park