Research, that is.  This report links genetic predisposition to impulsivity with later alcoholism.  This one ties the recent studies on the use of drugs to eliminate or reduce traumatic memories to the possibility of eliminating memories of contexts in which drugs have been abused in the past.  Substance abuse, according to research, is highly dependent on those contexts, and eliminating the memories might make relapse far less likely, it appears.  This one indicates that at least some teen pot use is tied to medical, rather than recreational, need.  Here’s the researcher:

“Bottorff said, "Marijuana is perceived by some teens to be the only available alternative for those experiencing difficult health problems when legitimate medical treatments have failed or when they lack access to appropriate health care".

The most common complaints recorded were emotional problems (including depression, anxiety and stress), sleep difficulties, problems with concentration and physical pain. The teens' experiences with the medical system were uniformly negative. The authors said, "Youth who reported they had been prescribed drugs such as Ritalin, Prozac or sleeping pills, stopped using them because they did not like how these drugs made them feel or found them ineffective. For these kids, the purpose of smoking marijuana was not specifically about getting high or stoned".”

Finally, this one from Australia found that newborns with serious drug withdrawal symptoms had increased over 40% since 1980.  Good thing we don’t have those problems here.