Health Effects of Marijuana

DDP Newsletter March 2019 Vol. XXXV, No. 2

In November 2018, Michigan became the 10th state to legalize recreational cannabis use. More than 200 million Americans live in states that have legalized marijuana for medical or recreational use, writes Alex Berenson (WSJ 1/4/19). One powerful push is the desire for tax revenue that might otherwise go to neighboring states. The New York City Comptroller’s Office estimated that legalizing marijuana for persons over age 21 could yield $1.3 billion annually at State and local levels. The Comptroller also touted reduced costs of law enforcement and the societal benefit of having fewer people, especially young black males, damaged by the impact of a criminal conviction (tinyurl.com/y68cjevf). E-mailed tips on the best cannabis stocks to buy anticipate more widespread legalization.

Advocates of legal marijuana have long asserted that it is less harmful than tobacco or alcohol. Opponents of a proposed Arizona Medical Association resolution to “promote educational efforts at least as strong as those for tobacco to inform the public about the dangers of marijuana” stated that research was needed to “back up strong recommendations,” and that dangers are “anecdotal.” This reminds me that the AMA resisted declaring tobacco to be a  hazard—cigarette ads ran in JAMA while my grandfather, who had an 8th grade education, knew they were “cancer sticks”—until evidence became too powerful to deny.

Because the DEA classifies marijuana as a Schedule I substance, illegal for all uses, medical claims have not been properly studied. Researchers in Arizona were unable to obtain the substance, as the only government-controlled legal source refused to supply it. Nevertheless, Arizona patients with a qualifying condition can get a medical marijuana card on the recommendation of a licensed Arizona physician, and legally buy a package from a licensed dispensary (tinyurl.com/y873fqv9). They have a “right to try” a product of unknown dosage and purity.

While the number of cannabis users has not increased greatly, the number of heavy users has been soaring. Between 2006 and 2017, the number of daily users increased from 3 million to 8 million Americans. Also, the potency is much greater. The amount of THC—delta-9-tetrahydrocannabinol, the psychoactive component—was usually less than 2% in the 1970s, and is routinely 20–25% now, thanks to sophisticated  cloning techniques.

Is “reefer madness” real? Or is it just that people with pre-existing problems are self-medicating? Sobering facts about mental health and marijuana:

  • The percentage of young adults in the U.S. diagnosed with serious mental illness (7.5% in 2017) has doubled since 2008 (https://tinyurl.com/yd933ocy).
  • Teenagers who smoke marijuana regularly are about three times as likely to develop schizophrenia; the higher the use, the greater the risk (ibid.).
  • According to a 2010 review, 27% of people with schizophrenia had been diagnosed with cannabis use disorder. And despite its reputation for making users relaxed and calm, cannabis appears to provoke many of these patients to violence (ibid.).
  • In a Swiss study of 265 psychotic patients, young men with psychosis who used cannabis had a 50% chance of becoming violent over a 3-year period (ibid.).

The neuropsychological effects of cannabis, aside from mental illness, occur in all stages of life, with particularly devastating effects on the maturing brain in childhood and adolescence. Marijuana overactivates the endocannabinoid system, causing effects that  include distorted perceptions, psychotic symptoms, difficulty with thinking and problem solving, disrupted learning and memory, and impaired reaction time, attention span, judgment, balance, and coordination. THC suppresses neurons in the information-processing system of the hippocampus, thus learned behaviors, dependent on the hippocampus, also deteriorate, according to the American College of Pediatricians (ACPeds) (tinyurl.com/y32y2xcl). Measurable consequences include:

  • an average drop of 8 IQ points between age 13 and 38 in heavy users in teen and adult years, compared with no drop in never-users;
  • a significant decrease in verbal memory for each 5 years of cannabis use;
  • structural abnormalities in gray matter on brain magnetic resonance imaging (MRI);
  • abnormalities in prefrontal cortex function and decreased size of working memory areas shown on functional MRI; and
  • impaired performance in verbal memory, processing speed, and executive function, worse with greater cumulative exposure (tinyurl.com/y6kg4ocn).

Cannabis is a known teratogen, yet many dispensaries recommend it for morning sickness. “Only once has a known teratogen like cannabis been marketed globally. That was thalidomide,” said Dr. Albert Reece, professor of medicine at Edith Cowan University. Even if a  mother discontinues cannabis use on discovering that she is pregnant, the infant would continue to be exposed to cannabinoid effects for several months, during critical organogenesis. The father’s cannabis use may be even more damaging than the mother’s. A spectrum of congenital neurologic impairments is seen, including some that mimic autism, and many cardiac and gastrointestinal anomalies such as ventricular septal defects and gastroschisis (BMJ 8/3/18, https://tinyurl.com/y6z9rvug).

Marijuana contains many of the same compounds as tobacco. According to ACPeds, smoking marijuana is more harmful than tobacco because it contains more tar and carcinogens than tobacco, and because marijuana smokers tend to inhale more deeply and for a longer period of time. Its many other health effects include:

  • chronic cough, respiratory infections, emphysema, and lung cancer;
  • a nearly five-fold increase in heart attack risk in the hour after smoking;
  • an increased risk of testicular cancer;
  • a doubled risk of involvement in an auto crash; and
  • an increased risk of stroke (26%), heart failure (10%), and sudden cardiac death, as presented at the American College of Cardiology’s 2017 scientific session.

Marijuana growing is also damaging to the environment. Illegal farms in California are contaminating land and water with banned fertilizers and deadly pesticides (https://tinyurl.com/y6lmu2db). Denver’s legal indoor pot farms could double the city’s production of smog-forming volatile organic compounds (Science 1/25/19).

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