Green’s Dictionary of Slang

(drugs) an addiction to associating with drug-users and being around drugs, rather than an addiction to any particular drug; usu. said of drug dealers.

1959		W. Burroughs Naked Lunch (1968) 33: Non-using pushers have a contact habit, and that’s one you can’t kick.
1969		R.R. Lingeman Drugs from A to Z (1970) 69: contact habit Vicariously experiencing some of the effects of drug addiction though not oneself addicted; said derisively by addicts of pushers and narcotics agents.
1971		E.E. Landy Underground Dict. (1972).