My Turn: No proof of causation in anti-pot column

For the Monitor
Published: 2/25/2019 12:15:12 AM

Michael Breen, a retired police lieutenant, published an essay in the Monitor on Feb. 18 warning readers that marijuana use has resulted in an increase in mental illness and violence.

As a physician, I do not agree with his conclusions, although there are a few areas of agreement that the public should know about.

Children, adolescents, pregnant women and patients with serious mental illness should not use cannabis except under specific medically defined circumstances. I also agree that we should use science and not bias to make important public policy decisions.

I am not going to refute every misleading statement in Breen’s essay, but I will explain what science and the evidence tells us.

There is a very important difference between correlation and causation. The fact that “people who used cannabis in 2001 were almost three times as likely to use opiates three years later” is a correlation. I would guess that this group in 2001 also used caffeine, alcohol, cocaine and maybe even chocolate correlating with later opioid use. Causation is different. Causation means that cannabis or caffeine use caused this population to use opioids. This is not supported by science.

In fact, there is clear evidence that in states with legal medical marijuana, people substitute cannabis for opioids, sedatives, heroin, alcohol and other far more dangerous substances, which has resulted in a 24.8 percent reduction in opioid related deaths. This, too, is a correlation rather than proof of causation.

Similarly, Breen’s essay distorts the research on schizophrenia, implying a causal link where none has been established. The 2017 report of the National Academy of Science, Engineering and Mathematics (NASEM), which Breen cites, stated only that there is “substantial evidence of a statistical association between cannabis use and the development of schizophrenia or other psychosis, with the highest risk among the most frequent users.” This shows a correlation but not causation.

Persons with schizophrenia have a greater incidence of substance use disorder, whether involving cannabis or another drug. In fact, the NASEM report further states that among patients with schizophrenia, there is a statistical association between a history of cannabis use and improved cognitive performance. That does not, however, mean that cannabis use actually makes people with schizophrenia smarter.

Cannabis is still relatively contraindicated in people with schizophrenia, given evidence that it can trigger or exacerbate psychosis in that population.

I would like also to address the recurring claim that increasing concentration of THC in available products is somehow a warning of unknown dangers. Understand that one “puff” of 20 percent THC cannabis is the same as four puffs of 5 percent. It is the dosage, not the concentration of THC, that regulates the effects of cannabis.

Adult users of cannabis can titrate their dosage to a desired effect.

With regard to the reported increase in crime in Colorado and Washington, when compared to similar states without legalization, crime rates are lower than expected. It’s easy to jump to conclusions and bend facts to support your personal beliefs. But we must do better, putting in the effort to understand the context and meaning of correlations.

Finally, let’s look at the risk of cannabis causing an epidemic of mental illness, paranoia and violence. Medical researchers use Post-Marketing Surveillance Studies (PMSS) when any drug comes to market in the United States. This is when a drug is used by millions of people rather than the thousands that are included in early studies. Harmful effects are reported and if a drug is found to be dangerous, it is taken off the market.

Given the abundance of studies on the health risks of cannabis, we could say that there has been the equivalence of many decades of PMSS conducted on adult use of cannabis. The result? There has been no epidemic of mental illness or violence resulting from cannabis use by adults.

According to the most recent Gallup poll, 66 percent of Americans favor legalization of cannabis. We must allow consenting American adults to decide when and how to use cannabis, just as they have done with alcohol and tobacco – two far more dangerous substances.

(Dr. Gilbert Fanciullo practiced anesthesiology, pain medicine, and hospice and palliative medicine in New Hampshire for more than 20 years. He is an emeritus professor at the Geisel School of Medicine at Dartmouth and continues to serve on various New Hampshire boards and committees. He is a founding physician member of Doctors for Cannabis Regulation and is chairman of the board of Prime Alternative Treatment Centers. The opinions expressed in this article are Dr. Fanciullo’s personal opinions and in no way reflect the opinions of Dartmouth or boards in New Hampshire.)

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