Rather than getting into the cultural or media criticism of the Frum–Riggs–Frum–Sullivan fracas over cannabis policy, perhaps it makes more sense to try to separate out the knowns and identify the unknowns. Experts on the question see open questions where passionate amateurs are most dogmatic about the answers.
1. Cannabis dependency is rarely as bad as severe alcoholism, but it can be plenty bad enough, and it isn’t very rare, especially among those who start – as most users now do – in their middle teens. (A sixteeen-year-old who goes beyond experimentation has about one chance in six of winding up a heavy daily user for a period of months or years.)
2. Most users – and even many frequent users – don’t go on to diagnosable abuse or dependency. There is little evidence of lasting damage from use that isn’t both heavy and chronic. It would be a mistake to attribute all of the suffering of even the heavy, chronic users to cannabis, as opposed to the social circumstances and personal traits that lead them to acquire and maintain the habit. But it would be equally a mistake to ignore their self-reports that cannabis is a source of trouble in their lives.
3. For the non-abusing majority of users, cannabis is a fairly harmless pleasure. For some of them, cannabis use lastingly enhances their lives by broadening their range of experience, deepening their appreciation of the arts, and enhancing their creativity by teaching them a new way of thinking. Very little is known about these phenomena in any systematic way, partly because the science is hard and partly because of the constraints and incentives that influence research.
4. Making marijuana cheaper, more available, and less risky to use will tend to increase both the prevalence of use and the average quantity per user, thus increasing the number of problem users.
5. Legalization will make marijuana cheaper – under most designs, very much cheaper – as well as more available and less risky to use.
6. Under contemporary social conditions, it is virtually impossible to make a commodity simultaneously easy for adults to get and hard for minors to get. No non-hand-waving argument exists to show that legalization will somehow reduce prevalence among the young; the mass of evidence and logic points the other way.
7. Among the consequences of cannabis use under current conditions among poor minority youth, being arrested is more common than developing a chronic substance abuse disorder.
8. The consequences of arrest – especially a first arrest for a young black male – can also be quite bad.
9. The cannabis market is an important element of illicit drug dealing generally in dollar terms – about $15 billion a year in criminal revenues in the U.S., or perhaps a quarter of total drug revenues – but only a modest contributor (less than 10%) to drug-related incarceration. Legalization would be expected to diminish the earnings of Mexican drug traffickers noticeably, but would hardly put them out of business. Violence in Mexico would probably go down some, but not much; the error band around that estimate is wide.
10. Cannabis is an increasingly downscale drug. A majority of the days of cannabis use involves people with less than a high-school education. But most of the discourse about cannabis involves upscale speakers and is addressed to an upscale audience, and speakers and audience alike tend to assume falsely that their experience, and that of their peers, is typical. Yes, pot has been intimately linked to jazz culture, but the high-school dropout who spends every day stoned is very unlikely to know, or care, what Thelonious Monk did for a living, and may be more in need of learning how to reason clearly than of lessons in going beyond linear thought.
11. The United States is among the world leaders in cannabis use and abuse. That is not the case for alcohol; most prosperous countries drink more than we do.
12. Even if legalization greatly increased cannabis abuse, alcohol would almost certainly remain the #1 intoxicant in terms of hours under the influence, numbers of abusers, personal and health damage from abuse, and social damage, especially violent crime, from intoxicated behavior. So those concerned about drug abuse, and especially drug abuse among the young and the poor, should keep their eyes on the main chance.
13. The interactions between alcohol and cannabis consumption, if both were legal, are unknown. Cannabis legalization could decrease the prevalence of heavy drinking and the damage it does, or increase it. This is not question that can be convincingly answered by abstract reasoning, or by information collected under prohibition. It’s an open empirical question, and – since the effects, for good or ill, of cannabis legalization on alcohol abuse could easily swamp the gains or losses with respect to cannabis use, abuse, and trafficking – the answer ought to matter. [UPDATE: David Frum picks up on this point, but seems to me to miss a logical step.]