Professor Yasmin Hurd, USA, will present the Keynote Lecture at the 37th ECNP Congress in Milan. She is the director of the addiction institute within the Mount Sinai Behavioral Health System as well as the Ward Coleman chair of translational neuroscience and professor of psychiatry and neuroscience at the Icahn School of Medicine at Mount Sinai in New York. Her research exploring the neurobiological effects of cannabis and heroin has significantly shaped the field. She recently spoke to the ECNP press officer, Tom Parkhill.
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TP (Tom Parkhill): Let me start by just asking you a little bit about yourself. Where are you from? What brought you into science? How did you end up working on recreational drugs?
YH (Yasmin Hurd): I was born in Jamaica. My family moved to New York when I was a young teenager. I love both places. I also worked at the Karolinska Institute in Stockholm, and I got my doctorate there. While there I went from assistant professor to professor. I think my journey to studying the neurobiology of drugs comes from my initial studies at the Karolinska where I worked with Urban Ungerstedt. He was interested in neurodegenerative disorders like Parkinson's disease. They had mapped the catecholamine system and developed an animal model for Parkinson's. We were studying dopamine because it's the dopamine neurons that are lesioned in Parkinson's. In teasing out the dopaminergic system we would use pharmacological approaches using amphetamines and cocaine, because those are indirect agonists. I saw that those drugs were so powerful in changing behaviour, and that’s how I got started in studying the neurobiology of drugs.
And how long have you been working on this field now?
Well, now over 25 years, really, the time goes by really quickly.
I saw that you were involved in a press conference in early May at the American Psychiatric Association meeting. You were talking about the types of cannabis and how much stronger cannabis is nowadays.
Yes, the problem is that we have added another very potent, intoxicating psychoactive agent into our society, and we are treating it as if it's completely benign. The original cannabis plants only had 2%, or perhaps 4% THC (tetrahydrocannabinol). That’s very different from the THC and other cannabinoid products being sold today. Dose does make a difference. Pharmacology is pharmacology, biology is biology. The more potent you make the chemical that binds to the receptor that induces the high, the more concentrated the chemical and the more powerful the effects. We see these stronger effects happening, especially in young people, and that to me is very sad. I think that many people have begun to think that cannabis is equivalent to say, alcohol or tobacco. You can allow the freedom for adults to be able to consume what they want to consume, but that's doesn't mean that you should go to the other extreme, and permit the use of highly concentrated, highly toxic products. And to me, what is happening is upsetting the balance between whatever adults need or want, and the growing public health impact.
About half the states in the United States now allow recreational cannabis use. And of course, we've just seen recently Germany and Canada have also approved recreational use. So it seems that there’s a liberalisation in the air.
Yes, but this is the problem. I think legalisation wasn't the real issue because I don't believe that people should be in prison for substance use. I’d prefer we use that money to help people get treatment, to get their lives back. To me it seems naïve, because they compare what cannabis used to be, and not to what is now available. This is actually a sort of ongoing research on our society, because we are using all these new products that no one has tested. Legalisation is not the issue, it's that we are leaving this to the unregulated market without considering the potential health impact.
Can you see any way that this can be regulated? Previously it was regulated by being banned.
That's tough to do when you know the horses have already left the barn. Products even up to 90% THC concentrate are being consumed. It's crazy. How do you bring that back when you've made people think that this concentration is what they need in order to get that big high? So, is it possible to regulate and use some of the knowledge we've gained from other markets? Yes. I think though it's going to be difficult because right now the market is in a way like the Wild West, especially in the US, because every state does what it does and there are no federal regulations that guide everyone. We'll see what happens in Germany. Canada had a different rollout than the US in terms of how they legalised, which I think helped.
One of the other things that you've worked on is using CBD (cannabidiol) to control heroin addiction. Can you tell me a little bit about that?
It's funny, because people think that I'm anti-cannabis. I'm not anti-cannabis. When we looked at our data on the developmental effects of THC in animal models, we saw that it negatively impacts opioid sensitivity when they became adults. Back then, CBD was not popular, no one knew much about CBD, and I just wanted to look at another cannabinoid. And when we looked at CBD, it actually did the opposite to THC. We saw that CBD reduced heroin-seeking behaviour in our animal models. It took me a very long time to convince people that CBD may be beneficial and to get a paper published and get grants. But the question was, can it work in humans, because that's what we're trying to develop medications for. Even back then we understood that CBD (unlike THC) didn't have the negative effects on mental health you see with higher potency THC. So we did two small pilot clinical studies in our human opiate users and it replicated what we saw in our animal model.
We're now running two larger clinical trials. The first one using neuroimaging studies, to try to understand the neurobiology in humans; the second to see what it looks like for people in the real world, not just as part of a lab study. For me the question isn’t “is cannabis bad?” It’s “are there components of the cannabis plant that might have medicinal value?” And the answer is, “absolutely!” But it's also important to realise that the endogenous cannabinoid system is complex and there is a lot that we still don't understand.
So obviously with the huge problems there's been over opiate abuse, particularly in the United States, this might be another weapon; it changes the balance a little bit. You say you're doing larger trials at the moment. Presumably you would then have to look at trying to bring something to the market.
Yes. I don't know if I care about the particular product, but do I care to understand if CBD can get FDA approval for treatment of opiate use disorder since, as you said, we have a huge epidemic opiate crisis. We need more treatments and I hope that CBD will be one of them, but the data will tell us. We saw in our human-study participants that it also reduced their anxiety, and that's one of the ways it might be working – decreasing stress reactivity, reducing the cues that trigger craving, anxiety, decreasing stress hormone cortisol levels. So for me it is another arsenal for clinicians to use to treat a very deadly disorder.
One of the things that you've also been looking at is pregnant mothers taking cannabis and the effect on their offspring. I think it wouldn't surprise most people to see some effect, but what have you found?
These are our cannabis studies of what happens during pregnancy. I just want to emphasise that these studies are not about penalising women who may use cannabis. It's about giving people knowledge. There are two developmental windows that I study in regard to the developmental exposure to cannabis, one of them is adolescence and the other is prenatal. Our team does translational research, so we use both animal models and human models to understand causality. We study women who had used cannabis while pregnant, and we have also been following their kids (this work is with my colleague Yoko Nomura, with whom we’ve been working on this for many years now). As you said, many things can impact during pregnancy. There can be excessive stress during pregnancy and we can see that both cannabis and stress impact – I will say “placental health” for the lack of another expression – because it changes the RNA, the gene expression signature, and it changes it in a way that's very interesting in terms of huge changes in the immune system. We can track their kids and we can see that the gene expression patterns in the placenta actually predicted children's future behaviour. When we give pregnant rats THC, we can track this in the placenta, and we can track this in behaviour over time.
So, studying early development for me is important because we know that sets the foundation for psychiatric risk later in life. So can we start to identify biological patterns which might help people earlier in their life rather than wait until a condition is fully expressed, perhaps in a way that we can’t treat successfully (at least for now). One of the things also that our prenatal studies and adolescent studies tell me is that these changes are really mediated by epigenetic mechanisms; and unlike genetics, epigenetic mechanisms can be reversed. So I really try to emphasise that these early life events do not have to be deterministic. With our animal models we can prove causality, but they're not deterministic outcomes for humans.
Do you have any closing thoughts?
I think that we need to be better advocates for science to the public. I think that as a group, scientists tend to communicate with each other; sometimes there’s a lot of infighting, and often we forget the bigger picture – which is that it’s not about us, it's really about our society and how science can help improve health. That is really critical. Let's make sure that we are talking to society, and that we're working together to improve health.
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Professor Hurd is the Keynote speaker at the 37th ECNP Congress in Milan. Her Keynote Lecture, The vulnerable brain: pathways to and from addiction, will be presented on Saturday 21 September, at 15.15-16.00 CEST.