Last month New York became the 15th US state to legalize recreational marijuana. People can now possess up to 3g, smoke it wherever they’re allowed to smoke cigarettes, and grow their own.
This is a big win for racial justice. New Jersey was the first state to make a racial-justice-based argument for legalization (my colleague Jeff Zymeri and I covered the debate back in college.) New York followed its neighbor’s footsteps.
Now the question remains: should you smoke cannabis now that it’s legal?
I talked to three experts on how cannabis consumption is related to one’s cognitive abilities.
Cannabis and IQ
“The short-term evidence is pretty strong,” said Nicholas Jackson, a statistician at the David Geffen School of Medicine at UCLA who has studied the association between marijuana use and intelligence. “If you have someone who is regularly using marijuana, we would expect them to perform poorly on tests of memory or intelligence, particularly during that period when they are regularly using marijuana.”
Long-term, the answer is more complicated.
In 2012, Madeline H. Meier, a psychologist at Arizona State University, and her team published a widely-cited longitudinal study documenting neuropsychological impairment among persistent cannabis users—defined as smoking 4 or more days per week—who started smoking in adolescence. By the time they were 38, they had lost about 6 IQ points. By contrast, non-users’ IQs had increased slightly.
And it was not just IQ—the study found that processing speed, memory, and executive functioning were all affected. (Their friends noticed that the stoners had memory and attention issues, too.) The researchers were able to rule out other explanations for the cognitive impairment: the impairment still appeared when the researchers controlled for the confounding effects of social class, hard-drug or alcohol dependence, years of education, and mental illness.
The results suggest that cannabis does have neurotoxic effects. (Animal studies also show this.) Now we want to know: does weed cause cognitive impairment, or is there some common factor that explains both the impairment and drug use?
Causality, Meier explained, is “the million dollar question.”
“We can never firmly conclude that findings are causal. However, we can strengthen the evidence for a causal explanation,” she said.
One way to do that is to look for dose-response associations: the heavier a person’s marijuana use, the more cognitive impairment they suffer. Meier observed that relationship in her study.
Another way to shed light on causality is to consider alternative explanations. Maybe IQ deficits actually preceded cannabis use. But Meier’s study ruled out that explanation as well.
If you try to study the effect on a shorter time scale and with more abstemious stoners, you might get different results. That’s what happened when Nicholas Jackson and his team studied groups of twins, in which one twin used marijuana and the other didn’t, over about ten years. They found that while marijuana users’ intelligence declined over time, so did their abstinent siblings’. And they didn’t observe a dose-response relationship or causal ordering. The researchers suggested that IQ deficit and marijuana use could be explained by other factors, such as the subjects’ early childhood environment or familial-cultural deficits (e.g. less parental monitoring, less emphasis on scholarship).
Of course, Jackson’s findings don’t contradict Meier’s. The twins study was much shorter, and it defined marijuana users as those who had smoked thirty times in their whole life or daily over a six-month period. That’s pretty lightweight compared to Meier’s subjects, who’d been smoking almost daily for two decades.
“One of the things that gets misrepresented in the media is how much a person is using before we see that cognitive impairment,” said Meier. “It’s hard to answer that question as a result of the research that’s been done in part because of differences across studies in terms of how much cannabis people are using.”
So, we need more research. Especially as cannabis is becoming more and more potent.
But some things are clear: smoking cannabis will impair your memory and intelligence in the short-term (think: up to a month after use). And in the long-term, the association between marijuana use and cognitive decline is established, even if we don’t know about causation.
Changing the conversation
Everyone I talked to emphasized that the cognitive effects of cannabis are just one part of the picture.
“I’d like to think that the research we do on the possible effects of cannabis on psychological functioning and psychosocial functioning, like educational attainment, will be taken into account by policy makers,” said Meier, “but I recognize that there are lots of other issues that should be taken into account,” such as racial disparities in the criminal justice system.
For Meier, the real question is: “how do we take into account all these considerations, including reducing arrests and imprisonment for cannabis possession, especially among Black and Hispanic people, while also reducing risk for negative health outcomes?”
There are also questions about why people use cannabis.
“The current literature focuses on [the question] ‘is marijuana making you dumb?’” said Jackson. “It’s fundamentally ignoring the reasons why individuals may seek out drugs in the first place.”
“If we have a 14 year old kid who is regularly smoking marijuana, I would expect them to have intellectual deficits. But the question isn’t really ‘did the marijuana cause that?’ [but rather] ‘why are they seeking refuge in drugs?’”
“We have the same literature on tobacco and intelligence, and no one’s really positing that it’s tobacco use that’s harming intelligence,” Jackson continued. “In that literature, it’s pretty much accepted that it’s a conduct problem. It’s other early childhood environmental [factors] that make the individual more likely to have lower intelligence as well as choose to use tobacco.”
In the spirit of focusing on conduct, I spoke to Rubin Khoddam, a clinical psychologist who co-authored the twins study, about the role cannabis and other legal drugs, such as alcohol, can play in someone’s life.
“Just because it’s legal doesn’t mean it’s healthy,” Khoddam said. “In the same way alcohol has chronic effects, cannabis can also have chronic effects.”
But can substance use play a positive role?
“Patients can present with a lot of different goals. From my perspective as a clinician, my first job is to see what their goals are, if it’s abstinence, if it’s harm reduction,” he explained. “Harm reduction can come in the form of reducing cannabis use or reducing other substances that often lead to cannabis use.”
Sometimes you hear people say that they use cannabis and alcohol as forms of self-medication. But there are healthier ways to deal with stress.
“Part of what therapy and treatment is about is finding other ways that you’d be able to get that same benefit and anxiety release but through healthier alternatives that don’t have the same impact on your body, on your lungs, or potentially longer-term consequences,” said Khoddam.
“Do you have adequate coping skills for when you do feel high anxiety? What do you do to put money in your emotional bank account? Those are the factors that I would consider before advocating using weed as a first line choice for dealing with anxiety,” he added.
Any quick and dirty tips for those looking to cut down?
First is “urge surfing.” Cravings are like waves.
“It’s usually in that time between when the craving starts and when it peaks that people use because it feels like that craving…is going to go on forever,” Khoddam explained. “If you ride it out all the way to the top, you’ll see that the craving dissipates. If you never give yourself the chance to see that it goes down, you end up reinforcing and teaching yourself that there’s no way to escape from whatever the feeling is other than using.”
As you practice riding the waves and being an observer of your emotions, you’ll notice that the peak of the wave will get smaller.
Another strategy is DEADS: Delay, Escape, Avoid/Accept, Distract, and Substitute. Delay giving into the craving, escape the triggering situation, avoid or accept triggers, distract yourself, and substitute, like drinking seltzer instead of beer.
If you’re going to give into the craving and smoke cannabis, be smart about it.
“One thought is to select cannabis that has lower THC content,” said Meier. “That might protect a person, possibly, from some of the harmful consequences.”
Better yet—avoid frequent and long-term use, she added.
There are physical health risks in addition to psychological ones.
“There is some concern about vaping and where you get your vapes given [an increased incidence of] lung injuries in 2019. We think many of those lung injuries are from marijuana vapes that were in the black market,” Meier explained.
Carl Hart, a neuroscientist at Columbia University, just came out with a book in which he revealed that he uses heroin regularly. Here’s an excerpt from a New York Times article:
Dr. Hart argued that most of what you think you know about drugs and drug abuse is wrong: that addiction is not a brain disease; that most of the 50 million Americans who use an illegal drug in a given year have overwhelmingly positive experiences; that our policies have been warped by a focus only on the bad outcomes; and that the results have been devastating for African-American families like his own. Much of the blame, he said, falls on his own profession. “We in the field are overstating the harmful effects of drugs,” he said. “We have miseducated the public, and that is wholly un-American and wrong.” Critics of Dr. Hart — and there are many — call these assertions both wrong and dangerous. “He is fast and loose with the science to advance the case,” said Bertha K. Madras, a professor of psychobiology at Harvard Medical School and director of the Laboratory of Addiction Neurobiology at McLean Hospital in Belmont, Mass. “You don’t ignore the adverse consequences — the parents, the families, the spouses who’ve had to live and deal with opioid use disorder. Traffic fatalities, workplace errors, absenteeism, workman’s compensation, drug-fueled violence, school dropouts, drug-related crimes and murders. I just don’t see Carl ever wanting to address these things.”
Of course it’s possible that both Hart and his critics are right. It can be true both that the field overstates the harmful effects of drugs, and that Hart understates them.
I asked Khoddam what the media gets wrong about drug use.
“It oftentimes negates and underestimates all the factors that led to the addiction. Addiction isn’t the problem, it’s the solution,” he said.
“We have all used something ‘out there’ to make something ‘in here’ feel better,” Khoddam continued. “People avoid their emotions and their own experiences through a lot of different ways. The more we can get in contact with the universality and commonality of that experience, the more we can fight the stigma associated with drug use and substance use.”