What You Aren’t Hearing About Marijuana’s Health Effects – WSJ

Bertha Madras, a leading expert on weed, outlines the science linking it
to psychiatric disorders, permanent brain damage, and other serious
harms.

By Allysia Finley Follow
May 10, 2024 3:13 pm ET

Young people who smoked marijuana in the 1960s were seen as part of the
counterculture. Now the cannabis culture is mainstream. A 2022 survey
counterculture. Now the cannabis culture is mainstream. A 2022 survey
sponsored by the National Institutes of Health found that 28.8% of Americans
age 19 to 30 had used marijuana in the preceding 30 days—more than three
times as many as smoked cigarettes. Among those 35 to 50, 17.3% had used weed
in the previous month, versus 12.2% for cigarettes.
While marijuana use remains a federal crime, 24 states have legalized it and
another 14 permit it for medical purposes. Last week media outlets reported that
the Biden administration is moving to reclassify marijuana as a less dangerous
Schedule III drug—on par with anabolic steroids and Tylenol with codeine—
which would provide tax benefits and a financial boon to the pot industry.
Bertha Madras thinks this would be a colossal mistake. Ms. Madras, 81, is a
psychobiology professor at Harvard Medical School and one of the foremost
experts on marijuana. “It’s a political decision, not a scientific one,” she says.
“And it’s a tragic one.” In 2024, that is a countercultural view.
Ms. Madras has spent 60 years studying drugs, starting with LSD when she was a
graduate student at Allan Memorial Institute of Psychiatry, an affiliate of
Montreal’s McGill University, in the 1960s. “I was interested in psychoactive
drugs because I thought they could not only give us some insight into how the
brain works, but also on how the brain undergoes dysfunction and disease
states,” she says.
In 2015 the World Health Organization asked her to do a detailed review of
cannabis and its medical uses. The 41-page report documented scant evidence of
marijuana’s medicinal benefits and reams of research on its harms, from
cognitive impairment and psychosis to car accidents.
She continued to study marijuana, including at the addiction neurobiology lab
she directs at Mass General Brigham McLean Hospital. In a phone interview this
week, she walked me through the scientific literature on marijuana, which runs
counter to much of what Americans hear in the media.
For starters, she says, the “addiction potential of marijuana is as high or higher
than some other drug,” especially for young people. About 30% of those who use
cannabis have some degree of a use disorder. By comparison, only 13.5% of
drinkers are estimated to be dependent on alcohol. Sure, alcohol can also cause
harm if consumed in excess. But Ms. Madras sees several other distinctions.
One or two drinks will cause only mild inebriation, while “most people who use
marijuana are using it to become intoxicated and to get high.” Academic
outcomes and college completion rates for young people are much worse for
those who use marijuana than for those who drink, though there’s a caveat: “It’s
still a chicken and egg whether or not these kids are more susceptible to the
effects of marijuana or they’re using marijuana for self-medication or what have
you.”
Marijuana and alcohol both interfere with driving, but with the former there are
no medical “cutoff points” to determine whether it’s safe to get behind the
wheel. As a result, prohibitions against driving under the influence are less likely
to be enforced for people who are high. States where marijuana is legal have seen
increases in car accidents.
One of the biggest differences between the two substances is how the body
metabolizes them. A drink will clear your system within a couple of hours. “You
may wake up after binge drinking in the morning with a headache, but the
alcohol is gone.” By contrast, “marijuana just sits there and sits there and
promotes brain adaptation.”
That’s worse than it sounds. “We always think of the brain as gray matter,” Ms.
Madras says. “But the brain uses fat to insulate its electrical activity, so it has a
massive amount of fat called white matter, which is fatty. And that’s where
marijuana gets soaked up. . . . My lab showed unequivocally that blood levels and
brain levels don’t correspond at all—that brain levels are much higher than
blood levels. They’re two to three times higher, and they persist once blood
blood levels. They’re two to three times higher, and they persist once blood
levels go way down.” Even if people quit using pot, “it can persist in their brain
for a while.”
Thus marijuana does more lasting damage to the brain than alcohol, especially at
the high potencies being consumed today. Levels of THC—the main psychoactive
ingredient in pot—are four or more times as high as they were 30 years ago. That
heightens the risks, which range from anxiety and depression to impaired
memory and cannabis hyperemesis syndrome—cycles of severe vomiting caused
by long-term use.
There’s mounting evidence that cannabis can cause schizophrenia. A large-scale
study last year that examined health histories of some 6.9 million Danes between
1972 and 2021 estimated that up to 30% of young men’s schizophrenia diagnoses
could have been prevented had they not become dependent on pot. Marijuana is
worse in this regard than many drugs usually perceived as more dangerous.
“Users of other potent recreational drugs develop chronic psychosis at much
lower rates,” Ms. Madras says. When healthy volunteers in research experiments
are given THC—as has been done in 15 studies—they develop transient
symptoms of psychosis. “And if you treat them with an antipsychotic drug such
as haloperidol, those symptoms will go away.”
Marijuana has also been associated with violent behavior, including in a study
published this week in the International Journal of Drug Policy. Data from
observational studies are inadequate to demonstrate causal relationships, but
Ms. Madras says that the link between marijuana and schizophrenia fits all six
criteria that scientists use to determine causality, including the strength of the
association and its consistency.
Ms. Madras says at the beginning of the interview that she was operating on
three hours of sleep after crashing on scientific projects. Yet she is impressively
lucid and energized. She peppers her explanations with citations of studies and
is generous in crediting other researchers’ work.
Another cause for concern, she notes, is that more pregnant women are using
pot, which has been linked to increased preterm deliveries, admissions of
newborns into neonatal intensive care units, lower birth weights and smaller
head circumferences. THC crosses the placenta and mimics molecules that our
bodies naturally produce that regulate brain development.
“What happens when you examine kids who have been exposed during that
critical period?” Ms. Madras asks. During adolescence, she answers, they show
an increased incidence of aggressive behavior, cognitive dysfunction, and
symptoms of ADHD and obsessive-compulsive disorders. They have reduced
white and gray matter.
A drug that carries so many serious side effects would be required by the Food
and Drug Administration to carry a black-box warning, the highest-level alert for
drugs with severe safety risks. Marijuana doesn’t—but only because the FDA
hasn’t cleared it.
The agency has selectively approved cannabis compounds for the treatment of
seizures associated with Lennox-Gastaut or Dravet syndrome, nausea associated
with chemotherapy for cancer, and anorexia associated with weight loss in AIDS
patients. But these approved products are prescribed at significantly less potent
doses than the pot being sold in dispensaries that are legal under state law.
What about medicinal benefits? Ms. Madras says she has reviewed “every single
case of therapeutic indication for marijuana—and there are over 100 now that
people have claimed—and I frankly found that the only one that came close to
having some evidence from randomized controlled trials was the neuropathic
pain studies.” That’s “a very specific type of pain, which involves damage to
nerve endings like in diabetes or where there’s poor blood supply,” she explains.
For other types of pain, and for all other conditions, there is no strong evidence
from high-quality randomized trials to support its use. When researchers did a
“challenge test on normal people where they induce pain and tried to see
whether or not marijuana reduces the pain, it was ineffective.”
Ms. Madras sees parallels between the marketing of pot now and of opioids a few
decades ago. “The benefits have been exaggerated, the risks have been
minimized, and skeptics in the scientific community have been ignored,” she
says. “The playbook is always to say it’s safe and effective and nonaddictive in
people.”
Advocates of legalization assert that cannabis can’t be properly studied unless
the federal government removes it from Schedule I. Bunk, Ms. Madras says: “I
have been able to study THC in my research program.” It requires more
paperwork, but “I did all the paperwork. . . . It’s not too difficult.”
Instead of bankrolling ballot initiatives to legalize pot, she says, George Soros
and other wealthy donors who “catalyzed this whole movement” should be
funding rigorous research: “If these folks, these billionaires, had just taken that
money and put it into clinical trials, I would have been at peace.”
It’s a travesty, Ms. Madras adds, that the “FDA has decided that they’re going to
listen to that movement rather than to what the science says.” While the
reclassification wouldn’t make recreational marijuana legal under federal law,
dispensaries and growers would be able to deduct their business expenses on
their taxes. The rescheduling would also send a cultural signal that marijuana
use is normal.
Ms. Madras worries that “it sets a precedent for the future.” She points to the
movement in states to legalize psychedelic substances, for whose medicinal
benefits there also isn’t strong scientific evidence. Meantime, she says it makes
no sense that politicians continuously urge more spending on addiction
treatment and harm reduction while weakening laws that prevent people from
becoming addicted in the first place.
Appeared in the May 11, 2024, print edition as ‘What You Aren’t Hearing About
Marijuana’.
Her rejoinder to critics who say the war on drugs was a failure? “This is not a
war on drugs. It’s a defense of the human brain at every possible age from in
utero to old age.”
Ms. Finley is a member of the Journal’s editorial board.