i think the risk-taking behaviours of young men and boys are well documented and widely understood.
as a show of strength, and a demonstration of fearlessness, males have a tendency to want to show others and themselves that they are not scared.
just look at the language used around this forum - boasting about your epic drug use = "dicksizing".
drug consumption is tied in with machismo for a lot of guys. this goes for alcohol as well as all kinds of drugs. if you don't share someone's taste in drugs, or preferred dosage, a guy can be accused of being effeminate, weak, homosexual, etc etc.
"less of a man" in simpleton terms.
that's not to say that women don't also have reckless tendencies and a range of social pressures, but i think what leads people to drug use in the first place can be affected by gender.
i think the "male = risk taker" social force is stronger (in australia, at the current time) than the "good girls don't use drugs" stereotype/pressure. every individual case is different of course...and i'm usually very reluctant to draw stereotypical conclusions about gender and behaviour.
but i certainly agree that i've known more male drug users, and of course that the perceptions of the general public and medical community are skewed in the suspicion cast upon guys in relation to drug use/abuse. the demographic i imagine most likely to be prescribed medications with abuse potential are middle-aged and older women. i don't have any figures for this, just my observations.
this could be their inherent common sense and measured approach to their health, the trust they have built with their doctors, or perhaps a stereotype of restraint and responsibility in regard to these matters.
while there are probably less old ladies going home and crushing their meds and sniffing them or running them through a micron filter- than twenty-something males - it doesn't mean that abuse and addiction isn't likely to happen. i wouldn't be surprised if there was some kind of statistical evidence showing a greater potential for drug misuse amongst the male population, but it seems to go against most of our modern understandings of sexual discrimination.
there are a lot of outdated, ugly stereotypes responsible for this (woman as nurturer, etc) and myths perpetuated by the media. so rarely in the narratives put to us in the news, film and television etc is the drug addict presented as female. if so, it is usually represented as the fault of some man corrupting her.
this was a rambling response, but i hope it makes sense. great thread!