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Paging Dr. Riggs

Response to Dr. Paula Riggs, criticizing Dr. Gupta

Dr. Paula Riggs, a professor of psychiatry at the University of Colorado and an expert on addiction, has written an open letter to Dr. Sanjay Gupta criticizing him for airing the documentary “Weed” on CNN on August 11. She is obviously an intelligent and educated woman, and some of the points she makes are quite valid. Others are unfortunately fallacious. I have reproduced Dr. Riggs’ letter below, and posted my own responses below that.

Dr. Gupta –

I have always held you and CNN in the highest regard, which is why I’m moved to express my concerns (outlined below) regarding some of the material and messaging in the CNN documentary, “Weed,” aired last night. I’m sure you and CNN will give careful consideration to these concerns and other feedback from viewers, clinicians and scientists in addressing any misperceptions related to the information/messaging in the CNN documentary that may have an unintended, negative public health impact.

1. The documentary conveyed that habitual marijuana smokers were less impaired drivers compared to occasional smokers — based on CNN’s anecdotal demonstration that included two individuals. This is in contrast to a substantial body of research (Crean et al 2011 and others) showing that chronic, daily use, or near daily use, in adults is associated with impaired executive functioning and persistent neurocognitive deficits (abstract reasoning, verbal fluency, decision making, working memory) that last at least one month even with sustained abstinence. Moreover, the messaging in the documentary could certainly be construed as encouraging regular marijuana (daily or near daily use) versus occasional marijuana use, which could further increase the number of individuals meeting criteria for cannabis use disorder and/or addiction. More concerning is the suggestion that it’s safe to drive under the influence of marijuana while acutely intoxicated IF you’re a habitual or experienced marijuana smoker. This is not consistent with the significant increase in marijuana-related motor vehicle accidents and fatalities documented in Colorado and other medical marijuana states since 2009.

2. The documentary clearly promoted the use of smoked “medical” marijuana and did not mention alternatives, such as synthetic THC. (two examples: Marinol and Sativex)

3. The documentary did indicate that marijuana is “addictive,” stating that 9 percent (or 1 in 11) of individuals who smoke marijuana progress to addiction or dependence. However, CNN did not distinguish between adults and adolescents — who have been shown to have greater vulnerability to cannabis addiction. 1 in 6 adolescents who experiment with this drug progress to dependence and/or addiction (versus 1 in 10-11 adults).

4. The documentary created confusion about the potential benefits of Cannabidiol, also called CBD, versus the high THC content of most medical and recreational marijuana products. I was most concerned by the suggestion that cannabis may be neuroprotective (e.g, “build her brain”). This is in contrast to a large body of research showing marijuana to impair memory –especially working memory — and interfere with the ability to convert short-term to long-term memory. Chronic use of marijuana has been shown to destroy neurons, dendritic connections, white matter tracks in the hippocampus and other brain areas with high concentrations of cannabinoid receptors.

5. Although there are certainly individuals with medical conditions whose use of marijuana supports more research, the CNN documentary was scientifically imbalanced and irresponsible in suggesting positive health and psychological benefits for which there is little to no evidence. Anecdotal cases presented in “Weed” ranged from:

– enhanced creativity (n=1; Does CNN REALLY want to suggest this as a legitimate indication for “medical marijuana?”);

– miracle cure for intractable seizures in one child (n=1);

– PTSD/trauma (n=1). To suggest that medical marijuana is an effective treatment for PTSD/trauma/and/or “psychic pain” (as suggested in your reporting about the Holocaust survivor) undermines and disregards a very large body of research on effective treatments for PTSD and/or trauma with proven efficacy/effectiveness.

6. The many positive claims of health benefits associated with medical marijuana were not balanced by the scientifically known health risks associated with marijuana use -— regardless of whether it’s called “medical” or “recreational,” including:

– prenatal marijuana exposure, which has been shown to cause long-term deficits in memory, learning , attention, early-onset depression (by age 10), and onset of conduct problems/delinquent behavior and cannabis use by age 14. The strongest associations were with first trimester exposure, when women are less likely to be aware that they are pregnant. These findings were based on a 14-year longitudinal study comparing women who smoked less than 1 joint per day versus those who smoked more than 1 joint per day during pregnancy (Goldschmidt et al 2012 ). Research shows that 1/3 of THC crosses the placenta — and it’s important to note that the marijuana smoked by the pregnant women participants in this study more than 15 years ago was almost certainly far less potent than most medical marijuana products sold today.

(Dr. Riggs added this side note when sharing her letter with colleagues: “I’ve been asked to develop language for the product ‘warning label’ for marijuana products sold in Colorado, which will include: “Marijuana should not be consumed by women who are, or who may be, pregnant because of risks to fetal development.” Two members of Gov. John Hicklenlooper’s regulatory task force stated that some OB/GYN practices in Denver/Colorado are actually recommending ‘medical marijuana’ to patients experiencing nausea related to ‘morning sickness’ during the first trimester of pregnancy.”)

– significant increase in hospitalizations related to inadvertent marijuana exposure (ingestion of medical marijuana edibles) in children (infants-age 12) based on recent study published in theJournal of the American Medical Association. (Wang et al 2013)

– significant increases in the number of cases of cannabis hyper-emesis syndrome, a condition in which people cannot stop vomiting, (presenting to emergency department, complicating the course of withdrawal/detox) in Colorado and other medical marijuana states.

There is substantial evidence that marijuana is neurotoxic to adolescent brain development.According to the most recent Monitoring the Future Survey (2012) conducted at the University of Michigan, 45 percent of high school seniors nationwide (61 percent in Colorado) report lifetime use of marijuana. In Colorado and other medical marijuana states, marijuana use among high school students is considerably higher than national norms largely due to increased access to high-potency marijuana. Currently, one in 20 high school students nationwide, and one in 15 high school students in Colorado, are using marijuana at levels associated with an average eight-point reduction in their adult IQ and persistent neurocognitive deficits (Meier et al 2012; Pope et al 1998; Brook et al, 2008).

I consider this a public health crisis comparable to the impact of environmental lead poisoning associated with an average 7.4 point reduction in IQ with exposures of 10 micrograms per deciliter (Canfield et al 2003, NEJM).

Respectfully submitted,

Paula Riggs, M.D.
Professor of Psychiatry
Director of the Division of Substance Dependence
University of Colorado School of Medicine

My responses, point by point:

1. Dr. Riggs’ concerns about impaired driving are valid, but every piece of evidence she mentions is ultimately irrelevant to her conclusion.

The first study she mentions found problems with “abstract reasoning, verbal fluency, decision making [and] working memory” in chronic cannabis users, but none of those deficits (if true) necessarily affect driving safety. Secondly, she notes an increase in auto accidents in Colorado since 2009; while this is probably true (the latest study of the question has some methodological problems), the increase may in fact be caused by an increase of new cannabis users trying the drug as its stigma decreases in the Centennial State.

In the end her concern is valid, though not for any of the reasons that she states. The data on the dangers of stoned driving is mixed, and for that reason cannabis users are encouraged not to drive until the drug has worn off – or at least until we know more.

2. She is right to criticize the absence of any discussion of Marinol or Sativex. Whereas Marinol has been largely pooh-poohed by patients for its slow onset and alarming side effects, Sativex (a whole-plant extract of THC and CBD administered by aerosol spray) is a much better drug which deserves to be part of the national conversation.

3. Sunil Kumar Aggarwal does a great job of explaining why the “1 in 6 adolescents get hooked on pot” claim is fallacious. To quote from his recent post on Alternet:

The research supporting the claim is also based on faulty math. While the “1 out of 6” statistic does not appear anywhere in the text, figures or tables of the references (20021994), the only way to come to this number is by manipulating numbers. The study’s authors attempt to measure the “Cumulative Probability for Meeting Criteria for [Marijuana] Dependence” by a certain age does not follow users over time, and thus represents a survey-based snapshot of their lives in which they recollect their past use. This data, collected from 3,940 total users sampled of whom 354 were classified as dependent, allows for the inference that, by age 18, 5.61% or “1 in 17” marijuana users are at risk for dependence. It does not, however, allow for an analyst to add together dependence risk percentages from ages 10, 15, 16, 17 and 18 , to get  14.5% or “1 in 6.” If the same math were applied to all ages reported, you would end up with 162.24%.

4. Riggs shows with this point that she is way behind on the state of cannabis science. By declaring her outrage at the suggestion that cannabis could be neuroprotective, she reveals her ignorance of modern research which is well-summarized by chapter 4 of Marijuana: Gateway to Health by Clint Werner (which includes, among other citations, a declaration by the respected Scripps Institute that THC is more effective at preventing Alzheimer’s disease than any other known drug).

Riggs does have a point concerning the effects of cannabis use on memory; there is some support for the idea that heavy use can negatively affect long-term memory performance. Then again, there is also some evidence for the idea that cannabis use can improve memory. As with so many matters related to cannabis use, more research is needed in this area.

Regarding her claim that cannabis use kills brain cells, I can only assume that she is thinking of the research conducted by Robert Heath at Tulane University in the 1970s, because I know of no other evidence to support the notion that pot use damages the brain. Regarding the Tulane studies, they have been thoroughly debunked, notably by the National Center for Toxicological Research in Arkansas (thanks again to Clint Werner for providing the references).

5. Dr. Riggs finds methodological faults with Dr. Gupta’s documentary, and she gets no argument from me. By calling out three “n=1” studies featured in the documentary, she correctly points out that Dr. Gupta has not presented evidence which would likely survive peer review in an established medical journal. Dr. Gupta could rebut that an hour-long documentary is an inappropriate format to present a document subject to the same strictures as a scholarly article, but I’ll let him speak for himself.

Regarding Dr. Riggs’ final example in this point, she correctly points out that at least two drugs, Paxil and Zoloft, have been found effective in treating PTSD. But she declines to mention that both drugs have also been found to cause unpleasant side effects such as sexual dysfunction and weight gain in significant portions of users – which is a valid reason why combat veterans and other survivors of trauma may want access to alternative therapies like cannabis.

6. Finally, Dr. Riggs faults the documentary for not providing a more balanced review of both the harms and benefits of marijuana. Had this documentary been filmed in a historical vacuum, she’d have a great point; ideally, the show should have been two hours long, devoting an hour each to both the benefits and harms of this drug. But Dr. Gupta could quite rightly point out that the US government (through the National Institute on Drug Abuse) has devoted the past forty years devoting its considerable resources to amplifying the harms of smoking pot to full volume even while actively obstructing proposed studies of cannabis’ medical applications (see Cannabis Now issue 7 – now on shelves). In light of this greatly imbalanced national debate, devoting greater time to the benefits of medical marijuana is actually more fair.

Nevertheless, it is worthwhile to go through her specific points, because the evidence she chooses is instructive:

  • “pre-natal exposure of marijuana causes developmental and delinquency problems in children” – This is probably true; the evidence is not conclusive but nonetheless compelling. That is why Colorado will soon require a label on retail marijuana warning expectant mothers against using it.
  • “significant increase in hospitalizations related to inadvertent marijuana exposure in children” – this is quite true, and a problem worth taking seriously. The most likely cause is a proliferation of medicated brownies and other food items attractive to kids. While no case of fatal cannabis overdose has ever been reported and there is no evidence of any permanent damage done to children who eat marijuana, the potent and disorienting effects of large cannabis doses can nonetheless be a traumatic event for a confused child; that is why some lawmakers have called for mandatory childproof packaging in legal states.
  • “significant increases in cannabis hyper-emesis syndrome” – a fancy way of saying that ingesting too much cannabis can sometimes make you throw up. It is true that reported cases have risen in the wake of major reforms, but it should be noted that such reactions are rare; the majority of cannabis users experience a decrease, not increase, of nausea.
  • “substantial evidence that marijuana is neurotoxic to adolescent brain development” – this may be true, but the evidence is not as strong as Dr. Riggs suggests. She references a study conducted in New Zealand, for example, which found a correlation between chronic cannabis use by teenagers and an average 8-point drop in IQ in the same people 20 years later. But she fails to mention that this study has been heavily criticized, most notably by an article published in the same journal which found that the 8-point drop in IQ could just as easily be explained by socioeconomic or other confounding factors. Bottom line? Cannabis use may affect the adolescent brain in negative ways, or it may not. Until further research clears up the debate, I agree with Dr. Gupta, who has repeatedly stated that he intends to discourage his children from using cannabis until their brains are fully developed.
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