Well, that's not quite the way he put it, but it is much closer to the truth. Today the Office of National Drug Control Policy announced that a new report from the University of Mississippi's Potency Monitoring Project (PMP) "FINDS HIGHEST-EVER LEVELS OF THC IN U.S. MARIJUANA":
According to the latest data on marijuana samples analyzed to date, the average amount of THC in seized samples has reached a new high of 9.6 percent. This compares to an average of just under 4 percent reported in 1983 and represents more than a doubling in the potency of the drug since that time.
That increase is much less dramatic than the ones claimed by drug warriors, including ONDCP Director John Walters, over the years. In a 2002 San Francisco Chronicle op-ed piece, for instance, Walters asserted that "the potency of available marijuana has not merely 'doubled,' but increased as much as 30 times" since the 1970s. That jaw-dropping claim was based on the premise that "the average THC content of marijuana was less than 1 percent" in 1974, whereas "the THC of today's sinsemilla...ranges as high as 30 percent." As I've argued, the notion that the marijuana consumed in the 1960s and '70s was typically indistinguishable from ditchweed, more likely to give you a headache than get you high, is implausible, to say the least. But yes, if you take the shittiest pot from the '70s and compare it to the best pot available today, you will get a very high THC multiple.
After years of ridicule, the ONDCP seems to have thought better of such meaningless contrasts. Now it is, at least ostensibly, comparing apples with apples, although it's not clear how representative or comparable the PMP's "convenience samples" from marijuana seizures are. Referring to page 12 of the PMP report (PDF), NORML's Paul Armentano points out:
Average potency of domestic cannabis is under 5% and remains virtually unchanged over the past decade. The overall change in average potency comes from a spike in the potency and quantity of non-domestic cannabis seized....More than twice as many samples of imported cannabis are included in the analysis (1916 vs 852) compared to domestic seizures. Of course, if they factored the millions of ditchweed seizures made every year into the equation, average domestic potency would be near 1% THC.
Nevertheless, it is quite likely that average THC content of marijuana consumed in the United States has increased significantly during the last couple of decades as consumers have become more discerning and growers have gained expertise. The question is why better marijuana is a bad thing. Drug warriors like Walters assume that pot smokers will consume the same amount of marijuana regardless of its potency, which flies in the face of both research and common experience. With stronger pot, people can smoke less to achieve the same high, thereby reducing their exposure to combustion products. Yet the ONDCP inexplicably cites "an increased risk" of "respiratory problems" as one concern raised by higher THC levels.
It also tries the usual Anslingeresque scare mongering about marijuana madness, conflating correlation (between heavy pot smoking and depression, for example) with causation. Norah Volkow, director of the National Institute on Drug Abuse, cites "the possibility that the more potent THC might be more effective at triggering the changes in the brain that can lead to addiction," although she concedes that "more research is needed to establish this link between higher THC potency and higher addiction risk." (It's inconceivable, of course, that government-funded research would fail to confirm this link.) To bolster the idea that marijuana is more addictive today, the ONDCP notes that "16.1% of drug treatment admissions [in 2006] were for marijuana as the primary drug of abuse," compared to "6% in 1992." It does not mention that referrals from the criminal justice system account for a large share of treatment admissions, or that marijuana arrests have increased by more than 150 percent since 1990.