David Murray, special assistant to the director of the Office of National Drug Control Policy (the “drug czar’s” office) disagrees (here) with my views here and here) about the great marijuana potency scare.

I suppose I should be honored that someone in Murray’s position spent so much time responding to a month-old post on what was then a truly obscure weblog, though if Murray truly thinks I’m “a smart guy, from whom much can be learned” it’s too bad he is so intent on misstating my arguments to make me look like a fool or a scoundrel. And if he really found what I had to say “hard to figure,” he could have picked up the telephone; he has my number.

In fact, of course, Murray’s official position means that he isn’t allowed to look around for facts and then craft policies to fit them; he starts with a policy choice — cannabis must, at all costs, be kept strictly illegal — and has to find what facts and arguments he can to support it.

I criticized Murray’s boss, John Walters, for saying that “the potency of available marijuana has not merely ‘doubled,’ but increased as much as 30 times.” My estimate was, and is, that potency is up about a factor of three over the past generation.

(Technical note: The potency of cannabis is conventionally measured by its percentage of THC [delta-9 tetrahydrocannabinol], its primary psychoactive agent. That convention isn’t entirely accurate, since several other chemicals in cannabis are also active, and the nature of the intoxication probably varies with the ratios as well as the absolute levels, but the approximation is, as they say, close enough for government work.)

Murray’s attempt to show that I first denied pot had gotten more potent and then affirmed it is just a word game; I denied that it had gotten more potent to anything like the extent his boss alleged, and then reported my own estimate of how much potency had actually grown.

In criticizing that estimate, Murray repeats Walters’s original error: comparing an extreme value today with an average value in the past and citing the ratio of the two as representing an increase. Extremes must be compared with extremes, and averages with averages. The numbers Murray cites — aside from a completely implausible figure of less than one percent potency from 1975 — are actually quite consistent with my estimate of a threefold increase on average, from the range of 2-3% THC to the range of 6-9% THC. Nothing in my argument would change if the growth in potency had actually been fourfold, which seems to me about as far as the data could plausibly be stretched.

The important question is not whether cannabis is stronger, but whether users are getting more intoxicated or face a higher risk of dependency. Murray cites no valid evidence, and I am aware of no valid evidence, that either of those things is true.

The number of treatment episodes and emergency room visits is up. But so is the number of cannabis users, especially younger teenagers. The age at first use has been falling steadily. Self-reported use among middle-school students has more than doubled since 1991, while self-reported use among high-school seniors is up 50%. More users, and younger users, would generate more treatment and ER episodes even if the risks per user had remained constant.

There is good evidence that today’s cannabis users are using less per sitting of the more potent — and more expensive — drug than their parents did. The average size of a “joint” has fallen from nearly half a gram to about a quarter of a gram. Self-reported intoxication levels are unchanged. Murray makes fun of this finding, but why should we assume that kids are incapable of reporting how high they get, or that the relationship between actual intoxication levels and self-reported intoxication levels has changed over time?

Murray seems to think that drinking cognac is more likely to get one drunk than drinking beer, and uses that to “prove” that higher potency must lead to more intoxication. Been a long time since your last kegger, Dave? Beer has remained teenagers’ favorite form of alcohol, by an overwhelming margin, even as the pattern of drinking has tilted toward bingeing and drinking to get drunk. (And self-reported intoxication levels from alcohol have risen correspondingly.)

Price matters. Kids drink mostly beer largely because the tax structure makes beer a cheaper drunk than whiskey. (The best single means of reducing substance abuse among teenagers would be to increase the beer tax.) Cannabis potency matters less than (potency-adjusted) cannabis prices.

I’m old enough to remember acquaintances in college buying marijuana around 1970 for $25 an ounce. Today’s prices are considerably higher; the report “What America’s Users Spend on Illegal Drugs” (prepared for, and published by, the drug czar’s office) gives $296 as the average price of an ounce in 2000. (See Table 9.)

(Note that the report assumes a purchase unit of 1/3 of an ounce, compared to the one-ounce unit my classmates regarded as standard. Smaller purchase units don’t necessarily imply smaller consumption units, but they do provide a hint.)

Adjusting for inflation and a roughly three-fold increase in potency, that means that the real-dollar cost of a milligram of THC has been about constant over that 30-year period, by contrast with 80% decreases in heroin and cocaine prices.

Since Murray remarks that I use “the same arguments that are routinely offered by marijuana legalization advocates,” let me once again put my actual opinion on record (quoting from my earlier post):

”My view is that the risks [related to cannabis use] are substantially greater than most of my well-educated boomer friends believe. Taking the entire population of people who have used cannabis at least five times, the risk in that group of becoming a heavy daily cannabis user for a period of at least months is something like one in nine. Being a pothead isn’t nearly as bad for you as being a drunk, and it usually doesn’t last as long, but it’s still not a good place to be.

”That seems to me a strong enough reason to oppose the legalization of cannabis on any commercial basis; I hate to think what RJR and Miller Brewing (or whoever just bought Miller Brewing) could do if they had cannabis to market the way they now market tobacco and beer. In my ideal world, there would be no law against growing cannabis, using it, or giving it away, but selling it would remain banned. [Emphasis added]

Of course potency isn’t really the point; it’s merely a debating point. Would Murray or Walters, or any of the other drug warriors, support legalization of cannabis up to some potency limit, on the model of Prohibition-era “near beer”? Of course not. Why should they? My opposition to commercial cannabis sales wouldn’t change a bit if a potency limit were added, because people can get just as stoned on 3%-THC pot as on 9%-THC pot.

So why pretend that potency has anything to do with the real issues? There are solid arguments to be made against legalization of cannabis on anything like the current alcohol model. There are good arguments to be made against my preferred grow-your-own policy; that is, it has disadvantages as well as advantages. But the potency argument is just a bogey-man to scare the boomers into disregarding their own experiences, personal or vicarious, with pot. That old dog won’t hunt, Dave; give him a rest.

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact: