OUTLOOK CANNABIS come up against scepticism and regulatory constraints on the road to the clinic. /GETTY But at the same time, the many manufacturers that promote CBD-laden oils, lotions and foods as a panacea for various health issues, often with minimal regard for local laws or medical evi- dence, are putting CBD’s medical advocates TIMES ANGELES LOS in an uncomfortable position. “I get calls and e-mails all the time — not just from families, but from physicians who have no clue how to address the requests they get from patients,” DON BARTLETTI/ says Yasmin Hurd, director of the Addiction Institute of Mount Sinai in New York City. “It’s a real problem.” STUCK IN THE WEEDS The breakthrough approval of Epidiolex was driven by strong investment from GW Pharmaceuticals, as well as vigorous advocacy from families of children with epilepsy who had heard tantalizing anec- dotes about CBD’s effects from jurisdictions in which medical cannabis is legal. “About eight years ago, a patient’s father said he was hearing stories about families in Colorado and California who use high-CBD strains for their kids’ epilepsy,” says Devinsky. “He asked me to do a trial.” As a medical student, he had Cannabidiol oil has purported health benefits, including helping to relieve chronic pain. been taught the history of medicinal cannabis, including well-documented uses of the plant DRUG REGULATION by nineteenth-century physicians to treat sei- zures. Indeed, cannabis has been part of the clinical armamentarium for epilepsy for more than 4,000 years. From menace to Research on CBD in the 1970s and 1980s focused on its interplay with other cannabi- noids, and particularly THC. “Whereas THC can induce psychotic symptoms, impair cogni- medicine tion and make people anxious, CBD appears to do the opposite,” says Philip McGuire, a psychiatrist at King’s College London. Cannabidiol could offer an effective treatment for a variety The first clues that CBD might sup- of conditions. But the substance’s uncertain legal status is press epileptic episodes came from a small clinical trial2 in 1980. It was led by Raphael stalling serious investigation. Mechoulam, a chemist at the Hebrew Univer- sity of Jerusalem, whose work on the synthesis and biochemical characterization of cannabi- BY MICHAEL EISENSTEIN is classified by the US Drug Enforcement noids in the 1970s had led researchers to begin Administration in the same way as are heroin to explore the medicinal properties of CBD. A annabidiol (CBD) is an illegal drug and lysergic acid diethylamide (LSD) — number of other trials that explored the com- with no redeeming value. It is also a schedule 1 substances with “high potential for pound’s pharmaceutical properties followed, useful prescription medicine for epi- abuse” and “no currently accepted medical use”. although scientists conducting early forays into Clepsy, with considerable potential for treating This flies in the face of current evidence. CBD clinical research faced an uphill battle. numerous other conditions. And it is a natu- Numerous studies have shown that CBD F. Markus Leweke, a psychiatrist who special- ral dietary supplement or ‘nutraceutical’ with is a safe and non-habit-forming substance izes in mental illness at Sydney Medical School, countless evangelists in the health and wellness that does not produce the ‘high’ associ- Australia, recalls struggling for seven years to community. Although contradictory, all three ated with tetrahydrocannabinol (THC), the publish findings from a randomized controlled statements are true from different perspectives, main psychoactive component of cannabis1. trial that demonstrated that CBD might offer and clinical researchers are frustrated. In 2018, the US Food and Drug Admin- an effective treatment for psychotic symptoms “In New York City, you can go to a latte shop istration (FDA) determined that Epidi- in schizophrenia3. “We got about 15 rejection and get a CBD product, but if I want to do a olex — a purified CBD product developed by letters,” says Leweke. “And this is a paper that clinical trial, I’ve got to get a 2,000-pound safe GW Pharmaceuticals in Histon, UK — effec- has since been cited almost 500 times.” and go through six months of paperwork and tively reduces the frequency of seizures in Forty years on from Mechoulam’s initial licensing,” says Orrin Devinsky, director of the certain rare forms of paediatric epilepsy. work, extensive randomized controlled tri- NYU Langone Comprehensive Epilepsy Center This approval has heartened the cannabinoid als have decisively shown that this purified in New York City. Like the cannabis plant from research community, which has long rec- cannabinoid can profoundly benefit children which it is derived, CBD, a type of cannabinoid, ognized the medicinal potential of CBD but with certain epileptic disorders. “Over those S2 | NATURE | VOL 572 | 29 AUGUST 2019 ©2020 Spri nger Nature Li mited. All ri ghts reserved. ©2020 Spri nger Nature Li mited. All ri ghts reserved. CANNABIS OUTLOOK trials, we saw about a 26–28% reduction in compound through a particularly rigorous the irritability and anxiety of those with autism. frequency over placebo in all convulsive sei- test by comparing its effects with those of “Many parents wanted to keep their children on zures for Dravet syndrome and drop seizures amisulpride, a potent medication for schizo- it even if the seizures didn’t improve, because for Lennox–Gastaut syndrome,” says Devinsky, phrenia. “We saw a significant decrease in they’re calmer and sleeping better,” he says. who has led several such studies4,5. “Some of symptoms over time for both compounds, and And although cannabis been demonized the patients became, and remain, seizure-free.” CBD beat amisulpride in terms of side effects, as a gateway to more dangerous substances, Preclinical data from rodent and cell- by far,” Leweke says. The team also found a clue Hurd has found that it might actually contain culture studies have hinted at the possible to the mechanism by which CBD might exert its an effective antidote for potentially deadly benefits of using CBD to help treat disorders antipsychotic effects: treatment with CBD was addictions. After observing that rats with a that range from Parkinson’s disease to chronic associated with elevated levels of anandamide, heroin addiction were less likely to seek out the pain. The range of conditions in which CBD a cannabinoid produced by the body that seems opioid when treated with CBD, she began to is being tested might seem diverse, but it is a to offer protection from psychosis. investigate whether CBD might have the same compound with far-reaching, if poorly under- McGuire and his colleagues conducted a effect on people with an opioid dependency. stood, physiological effects. Antonio Zuardi, randomized controlled trial that showed that On the basis of an encouraging pilot study, a psychiatrist at the University of São Paulo in CBD can have an addi- Hurd and her team conducted a randomized Brazil, notes that something on the order of “We have tive effect when used controlled trial in 42 abstinent heroin users, 20 possible mechanisms of action have been very few with conventional who had avoided taking the drug for up to described to date for CBD. “These multiple double-blind, antipsychotic drugs10. three months after years of routine or heavy pharmacological effects may justify the wide randomized Together, they were use13. The researchers then exposed the par- range of possible therapeutic activities.” placebo- better able to control ticipants to drug paraphernalia and videos The mechanism of CBD’s action on controlled symptoms such as hallu- that showed heroin use — cues that normally cannabinoid receptors, at least, is well under- trials.” cinations and delusions provoke strong cravings in people with a stood. CBD can bind to the cannabinoid than could conventional dependency — and then measured participant- receptor CB1, which is the same receptor that medication alone. His team has received fund- reported responses and physiological indica- THC seeks out in the brain. Unlike THC, how- ing for a large, international trial to test whether tors of stress and anxiety. “Cue-induced craving ever, CBD restrains rather than activates CB1 CBD can be developed as a licensed medicine is associated with increased cortisol levels and signalling, and therefore doesn’t induce the for treating psychosis. increased heart-rate, and CBD reduced those,” psychoactive effects of its cannabinoid cousin. Anxiety disorders are another mental- she says. Participants receiving CBD also But CBD wears many hats. It seems to health condition that CBD has been shown reported lower levels of drug craving and anxi- mediate its antiepileptic effects by binding to to help alleviate. Zuardi and his colleagues ety relative to placebo group, and Hurd notes a protein called GPR55, which can otherwise used a test that simulates speaking in public to that the beneficial effects persisted for a week trigger the onset of seizures by promoting show that pretreatment with a single dose of after the final administration of CBD. the hyperactivation of neurons6. In addition, CBD can reduce the associated discomfort in CBD acts on receptors that mediate pain sig- people with social anxiety disorder11. A simi- A DIFFICULT DELIVERY nalling and inflammation, as well as at least lar effect has been observed in healthy people Despite its promise, CBD’s impact as a drug has one receptor for the neurotransmitter seroto- in anxiety-inducing situations12, and several been mixed. Importantly, it is relatively safe. 7 nin, 5-HT1A . Gabriella Gobbi, a psychiatrist researchers are exploring CBD as a means of The side effects most commonly associated and neuroscientist at McGill University in soothing social stress in people with autism with a high dose of Epidiolex include digestive Montreal, Canada, has found that CBD’s physi- spectrum disorder.