The drug czar's office, terrified lest parents be insufficiently terrified about the risks that their children will use cannabis, has a long, bipartisan history of overstating the drug's risks. (Of, course, there's a strong tendency on the other side to understate those risks, for example by denying that pot has any addictive potential whatever, but you'd like to expect better, rather than worse, behavior from federal agency.)

Consider, if you will, this factoid, from an "open letter to parents" signed by John Walters and run in 300 newspapers as part of the "anti-drug" ad campaign:

...more teens are in treatment with a primary diagnosis of marijuana dependence than for all other illicit drugs combined.

Now comes CESAR (the University of Maryland's Center for Substance Abuse Research, not by any means a generally dovish source in drug-war terms) with a little corrective fact: of all referrals (not broken out by age) for marijuana treatment, more than half come from the criminal justice system. And that fraction has been rising, reflecting another fact: marijuana arrests have roughly doubled over the past fifteen years, with the vast bulk of those arrests are for simple possession. Other studies show that for juveniles, most non-criminal-justice referrals reflect parental pressure.

It's a beautifully circular system: Step up enforcement against marijuana users, leading to more criminal-justice referrals to treatment. Tell parents cannibis is more dangerous than ever before, encouraging them to force their kids into treatment for even casual pot use. Then use the resulting increase in juveniles getting treated for cannabis as evidence of how dangerous the drug really is, supporting more enforcement and more propaganda aimed at parents to generate still more treatment referrals.

Cannabis, like any reinforcing drug, has some addictive risk. (See Anthony, J.C., Warner, L.A., & Kessler, R.C. (1994), "Comparative epidemiology of dependence on tobacco, alcohol, controlled substances, and inhalants: Basic findings from the National Comorbidity Survey", Experimental and Clinical Psychopharmacology, 2, 244-268.) The most recent comprehensive literature review summarizes the findings of the Anthony et al. study thus: A[n} ... estimate of the risk of meeting DSM-R.III criteria for cannabis dependence was obtained from data collected in the National Comorbidity Study. This indicated that 9 per cent of lifetime cannabis users met DSM-R-III criteria for dependence at some time in their life, compared to 32 per cent of tobacco users, 23 per cent of opiate users and 15 per cent of alcohol users." Hall W, Room R, Bondy S. Comparing the health and psychological risks of alcohol, cannabis, nicotine and opiate use. In: Kalant H, Corrigan W, Hall W, Smart R, eds. The health effects of cannabis. Toronto: Addiction Research Foundation, 1999, pp. 477-508.