Speaking of Psychology: Marijuana: The brain changer, with Krista Lisdahl, PhD
Teenagers and young adults who use marijuana regularly are at risk of significantly altering the structure of their brains, according to research by neuropsychologist Krista Lisdahl, PhD. In this episode, she discusses what this means for parents, youths and policymakers considering legalizing recreational and medicinal marijuana.
About the expert: Krista Lisdahl, PhD
Krista Lisdahl, PhD, is the director of the University of Wisconsin-Madison Brain Imaging and Neuropsychology (BraIN) laboratory. Lisdahl specializes in clinical neuropsychology, addiction, adolescent brain development and neuroimaging. With funding from the National Institute on Drug Abuse, she is studying the effects of marijuana use on brain structure, functioning and connectivity in adolescents and young adults.
Audrey Hamilton: The number of adolescents and young adults using marijuana on a regular basis is increasing and some states are legalizing recreational marijuana. But regulating its use among young people is a challenge that needs to be considered in light of scientific research, says neuropsychologist Krista Lisdahl. In this episode, she talks about why chronic marijuana use is especially toxic to teenagers’ brains – even more so now than a few decades ago. I’m Audrey Hamilton and this is “Speaking of Psychology.”
Psychologist Krista Lisdahl is director of the Brain, Imaging and Neuropsychology Laboratory at the University of Wisconsin-Milwaukee. Using Magnetic Resonance Imaging, or MRI, she studies the neurocognitive consequences of chronic drug use on the brains of teenagers and young adults. Welcome, Dr. Lisdahl.
Krista Lisdahl: Thank you. It’s a pleasure to be here.
Audrey Hamilton: Years ago, there was a television public service announcement aimed at teenagers that showed an egg frying in a pan. You remember that. An announcer saying “this is your brain on drugs.” Very dramatic. It was memorable to a lot of kids of that generation. Do you think people, specifically teenagers, really understand what marijuana use, specifically, can do to their brains and is it increasing among teenagers?
Krista Lisdahl: So, for the first question, do they understand what it really does to the brain, I would have to say for the vast majority, no, there’s not a good understanding. In fact, a lot of people that I talk to – it seems like they don’t even understand the concept that marijuana is a drug that gets in the brain – and that’s where the affects come from. A lot of times, the attitude is that, you know, marijuana is just an herb. Why would it affect you? It’s safe. As though it’s something like mint, you know, that it’s not a psychoactive drug.
The other question is, is marijuana use increasing among teens? We have seen an increase actually specifically in heavy, regular use, which is most alarming to me because that’s when we see more of the negative health effects. So, since we’ve had the highest rate since the 1980s, in the last five years or so it’s gone up from about two percent of high school seniors using daily all the way up to almost seven percent.
Krista Lisdahl: Daily. So there’s more teenagers using marijuana daily than they are using alcohol daily. And about 23 percent of high school seniors are using it in the past month and that’s now surpassed nicotine use and so it’s second only to alcohol.
Audrey Hamilton: Many jurisdictions amongst all of this are considering decriminalizing marijuana – not just medical marijuana – but recreational marijuana. What sort of information should policymakers have when they consider making this drug available to the general public?
Krista Lisdahl: Some of the things that I thought about in weighing the policy issues is the first question we need to ask is, “Is the current policy working in reducing marijuana use?”
Well, already we see that attitudes relating to marijuana have gotten softer and people for the most part, including teenagers, don’t see it as very dangerous. When we see those attitudes shift, we see marijuana use go up. And so, in some ways, this is not even tied to policy changes. It’s more about just the kind of culture the belief system surrounding marijuana. And so, in the states that have kind of looser beliefs about marijuana or believe that it’s safer are more likely to pass the legislation for medical marijuana or decriminalization or even legalization.
So that’s one question, is it actually working – our current prohibition policy? And a lot of people would say it’s not – it is somewhat effective at reducing use, but right now we see use going up either way with at least the majority of states still having prohibition.
The other question that people have to consider when making these decisions is, “Is the current policy potentially doing harm?” And we do see that with the Bureau of Justice Statistics about 250,000 adults being arrested for possession charges of marijuana. This does cost a lot of money. One of the bigger concerns brought up by some of my colleagues, including people like Dr. Carl Hart, is that there’s a very large racial bias in this, so African-Americans are four times more likely throughout the country to be arrested compared to Caucasians and federally, Hispanics are more likely to be arrested. They also get more severe sentencing. And so, one thing to balance out is is prohibition doing harm? There is an argument that it is doing some harm as far as racial discrimination and arrests and sentencing.
And so then the question is, “What are the alternatives?” So, a lot of people have come out to support decriminalization. And one of the strengths of that is that it gets rid of some of this criminal justice issue and the cost of putting people in prisons. America has more people in prisons than any other country. This isn’t my specialty, but it’s clearly an issue that needs to be addressed.
More on the public health side, that is my specialty, is if jurisdictions consider either decriminalization and especially legalization, they have to really get ahead of the legislation and before they even put it into place consider how they can prevent adolescent, an emerging adult. So, youth use. How are they going to prevent that? How are they going to get it – the people who need treatment? How well are they going to fund prevention and treatment? And then there’s other things like how are you going to limit advertising? How are you going to limit potency? How are you going to make sure that the marijuana’s clean and doesn’t have other things like mold in it?
Audrey Hamilton: So, what are some of the major changes that are happening in the brains of chronic marijuana users and how do they affect their mental abilities?
Krista Lisdahl: Yeah, so my areas are neuropsychology and neuroimaging and I’ve spent the last 15 years or so studying how chronic regular use – so the first thing is I need to define that. So that’s at least, at least weekly use all the way up to multiple times a day. And what we see is the bigger effects in cognition are in younger people. One of the reasons we think this is happening is that the adolescent brain isn’t mature until about the mid-twenties. There’s a lot of neurodevelopment going on in the connectivity, in the structure of the brain that really doesn’t peak about age 25. Now, people start using drugs around age 16-17 on average. It’s not an adult onset. The peak use is in teenagers and young adult years and if you start using before age 18, you’re at double the risk for developing a use disorder. And so, I consider addiction a teenage onset disorder. And so, I’ve looked at how chronic marijuana, repeated marijuana use effects these brains and we do see significant changes in verbal memory, the ability to control impulses, decision making, the ability to kind of hold information in mind and manipulate it, the ability to sustain your attention over time. And the other thing that we see is increased mood symptoms, including depression and anxiety and also increased problems with sleep.
Now, a lot of these things get better if people stop using, and in fact we have evidence that if teenagers stop using for at least a month, we see that their sleep quality improves and we also see that some of the cognitive functioning improves, although not all of it. And there is a longitudinal study showing that if you start before 18 again, using regularly, not just a couple times but at least once a week, that we see the biggest drop in IQ – eight points IQ loss –that’s very significant. And the people who use in their teens never as adults – even though they didn’t use as adulthood, never got back on the trajectory you would have predicted. Now, that study is by Meyer and colleagues. One problem with it is that in the end, there’s a pretty small sample size of the teenage regular use onset. And so, when you’re thinking policy, it’s not just the heavy users, although they drive the majority of the market and that’s why I’m concerned – and everyone’s talking about adults – but frankly, people start using in their teens and the heaviest users are in their teens and young adults.
So, if we change adult policy, we really need to make sure that we have all of the safeguards in place to protect use in teens. And I want parents and teachers and physicians to start taking marijuana use seriously in young people and really educate them that if they use regularly, they may be changing the structure of their brain and they may not reach their full potential.
Audrey Hamilton: Now Tetrahydrocannabinol, commonly called THC – I’m glad I got that out of my system – is the major psychoactive chemical in marijuana. Why is it important to consider the potency of these drugs?
Krista Lisdahl: It’s a really great question. What we’ve seen over the past 20 years or so is that the average THC content in marijuana joints was about five, six, seven percent. It is now up to 15 to 18 percent and they’re also making products for basically their burning oils down and purifying them down to almost 28 percent THC.
Now it’s possible that people could be smoking a joint with high THC content and just inhale less to kind of control that dose although we need more evidence that that’s what they’re actually doing.
The other problem of this, though, is that as they’re kind of creating these strains with really high THC, what’s happened is another component of marijuana called cannabidiol, is going down. And what we know is cannabidiol actually has opposing effects to THC in the brain and it seems to be neuro-protective. It actually reduces anxiety and there are some human studies that show if someone is smoking marijuana with high content of cannabidiol, then they have fewer cognitive effects both while they’re smoking and then a few days later.
We need more evidence to figure out, like, what is the safer ratio of THC versus cannabidiol. But, this is something that a lot of government agencies are really considering. So for example, the Netherlands are thinking about capping the THC levels at 15 percent and other folks like myself are really trying to push them to also consider increasing the minimum requirement of cannadibiol.
Audrey Hamilton: What about medical marijuana? Does that have a high THC count or is that regulated at all?
Krista Lisdahl: It – there’s different strains. You know, people basically sell and market these different strains. Some of them have very high THC content. Some of them have very low. There are some strains that are marketed as really high cannabidiol, like Charlotte’s Web, for example. Although, these aren’t regulated.
Krista Lisdahl: And it’s, it’s hard. Science hasn’t exactly gotten on board to test all of these and to look at the psychopharmacology. There are clinical trials that control the levels of THC and cannabidiol and I actually really strongly support that as far as the medicinal side goes, that science and medicine lead the way in this and we do clinical trials just like any other medication and that we don’t have parents out there trying to pick different cannabanoid oils and things like that for their children when there’s really very little evidence to back it on safety profiles and the therapeutic dose.
So, we really – we need more research and we need to get ahead of that. I actually think it’s slightly ridiculous that we just have people smoking pot that they get from growers as a medicine.
Audrey Hamilton: Now many people are under the assumption that marijuana is not addictive. You can’t be addicted to it. It’s just not like alcohol. It’s not like cigarettes. But, so is it?
Krista Lisdahl: There’s actually very strong evidence that marijuana is addictive and any, pretty much any scientists that are talking about policy, no one denies that it is addictive. What we see in the general adult population is of those who use marijuana, nine percent show a cannabis-use disorder. So, problems related and signs of addiction.
What we see in teenagers, however, is if you start smoking before 17, the rate is closer to 18 percent, rates of addiction. And actually, if you start smoking in more like 14, 15, you have even higher rates, like 25 percent who try it and become addicted. So there are these sensitive periods where you’re more likely to develop a cannabis-use disorder. With that said, people always like to put this within context. Alcohol is more addictive. About three-quarters of people who try nicotine become addicted. But it’s similar to other drugs that are legal – slightly less addictive than alcohol and nicotine.
Audrey Hamilton: Are there risk factors for who may become more addicted, especially among teenagers?
Krista Lisdahl: One of them is having comorbid psychiatric disorders. So, individuals with a diagnosis, for example, of schizophrenia or depression may have more problems related to their cannabis-use and thus more likely to develop cannabis-use disorders.
There’s also in African-American and Hispanic adolescents and young adults if they have a lot of arrests in their past – and this is where the criminal justice part of it comes in and that might actually getting rid of some of the criminal justice components might actually be protective against developing problems.
Some other risk factors are being very impulsive. Being someone who’s sensation-seeking, you may be more likely to try something like marijuana. But, sensation-seekers actually think about the consequences. The difference is if you’re impulsive you try something, you don’t really think about the consequences and those folks are more likely to develop dependence and use disorders.
Thankfully, the majority of teenagers don’t become dependence. There’s a huge segment – at least half that don’t even try marijuana or really other drugs.
We are trying to really figure out what puts someone on the track of trying it. That kind of first stage in really enjoying it and it being really rewarding and then going on and using it regularly, therefore kind of changing the structure of the brain and sensitizing the brain to the drug and then using compulsively and really showing a cannabis-use disorder.
So, there are some longitudinal studies right now. Really trying to figure that out so what predicts what trajectory you get on. And also, what’s so protective? We know that parental involvement, community norms that say that cannabis is harmful help reduce the likelihood of you using. And also being involved with a lot of other activities – especially physical activities and also religious activities are protective.
Audrey Hamilton: Great. Well, thank you Dr. Lisdahl for joining us.
Krista Lisdahl: Thank you.
Audrey Hamilton: For more information on marijuana use and teens, visit our website . With the American Psychological Association’s “Speaking of Psychology,” I’m Audrey Hamilton.