"Cannabis is not without harm but it's substantially less than alcohol and tobacco in terms of social harm," Room told the Herald Sun. He went on to add that teens are likely "better off" consuming both pot and alcohol instead of just alcohol. Room doesn't mean that people would substitute out alcohol for weed, and that this would improve things, he means that given that someone has had, say, five drinks, smoking pot would, on average, be a good idea for this person:
"If you are adding the cannabis to an equal amount of alcohol, then in some ways you'd be probably less likely to be aggressive but it's a bad idea to add it on if you want to drive a car."
The public health argument is one that gets made infrequently in defending the legalization of cannabis (medical marijuana has many defenders, but because it is often legalized separately, those tend to be separate discussions). Room has as much credibility in this discussion, because his articles tend to be of the "party responsibly or preferably not at all" variety, such as, "My drinking, your problem: alcohol hurts non-drinkers too," and "Cheers to health warning labels for alcoholic drinks."
That first title may contain a hint of Room's thinking: substances don't just affect the person using them, and marijuana can blunt the societal effects of alcohol.
"It makes sense to legalize marijuana in a controlled market," Room told the Herald Sun. "I think we need to have the discussion and it makes a lot of sense in terms of, among others, cutting down government costs to have a fairly highly controlled legal (cannabis) market and, while we are at it, tighten up the legal market of alcohol in the same way we tightened up the market of tobacco."
Prediction: Cannabis will be legal in at least five U.S. states and two South American countries within five years, and legal in 20 or more U.S. states and at least two European countries in ten years.