Isn't it weird how different genres of music apply to different drugs? I've also thought about how different decades feature different drugs (except weed has been featured in pretty much everone).
This is my take on it but I may be wrong since I haven't been around for that long. Correct me where I might have made a mistake.
'60s- Cannabis and LSD-25
'70s- Cannabis and Cocaine (later in the decade)
'80s- Cocaine, Cocaine, and did I mention Cocaine? Also, crack plagues the nation in the latter years of the 80's.
'90's- Heroin and Pharmaceuticals.
2000-2010- MDMA, Pharmaceuticals, and Disocociatives such as Ketamine
(By the way, these are merely my assumptions of the most widely-used or known substances, not the only drugs being used).