Scientists have engineered tobacco plants to produce five powerful psychedelic compounds normally found in other plants, fungi and animals in a single crop. They argue that using plants to manufacture the drugs would be simpler and more sustainable than existing processes, making research into therapeutic uses and production of future medicines easier.

at the Weizmann Institute of Science in Israel and his colleagues modified Nicotiana benthamiana plants using a technique called agroinfiltration, which involves using a bacterium to introduce genes from other organisms into a plant. The modified plant then makes the proteins encoded by those genes, but the DNA isn’t incorporated into the plant’s genome, so the effect is short-lived.

With the addition of nine genes, the plants were able to produce psilocin and psilocybin, usually found in mushrooms; DMT from various plants; and bufotenin and 5-methoxy-DMT, compounds secreted by the Colorado river toad (Incilius alvarius).

Plants could easily be altered permanently with changes that become inheritable, but doing so could be problematic, given that the compounds produced are commonly used as recreational drugs, says Aharoni. “It’s a little bit tricky if we have it inherited, and then people will ask for seeds,” he says. “We can do it also in tomato, potato, corn.”

The medical uses of psychedelic compounds are becoming more popular and better understood, says Aharoni, but harvesting them from natural sources risks populations threatened by habitat loss and overexploitation. The drugs are chemically synthesised for use in research, but producing them in tobacco plants, which are easily cultivated in greenhouses, would be much simpler.

The idea of growing drugs through pharmaceutical farming, or “pharming”, certainly isn’t new. Plant-produced protein drugs have been approved in the US since 2012, and as far back as 2002, maize has been modified to produce a pharmaceutical protein. Another research team used tobacco plants in 2022 to synthesise cocaine, discovering that it could produce about 400 nanograms of cocaine per milligram of dried leaf – about a 25th of the level in a coca plant.

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A single dose of LSD seems to reduce anxiety

About half of people with generalised anxiety disorder don’t respond to common treatments with antidepressants – but psychedelics may offer relief

at the University of Nottingham, UK, says around 25 per cent of prescription drugs are derived wholly or partially from plants, and there are massive opportunities to create “green factories” that can grow new compounds in greenhouses.

“If you want to understand something, you’ve got to be able to build something, so showing that you can make it in tobacco plants is useful,” says Fray. “As a technical accomplishment, to show that you understand the pathways and can do it, I think it has value.”

Roughly one year ago, thousands of people gathered in Denver, Colorado, for the largest psychedelic conference in history. The mood was electric, with most attendees confident that the US Food and Drug Administration (FDA) was on the verge of approving its first psychedelic drug.

But last week, the FDA dealt a devastating blow to supporters of psychedelic therapies. It rejected the hallucinogen MDMA as a treatment for post-traumatic stress disorder (PTSD), citing concerns about safety and the validity of clinical trial results. The decision is a pivotal moment for psychedelic science and raises questions about what – if any – future these drugs have in medicine.

The California-based company Lykos Therapeutics has published trials showing that MDMA, along with talk therapy, significantly improved symptoms of PTSD. The trials, which involved almost 200 adults with moderate-to-severe PTSD, found that between 33 and 46 per cent of those treated with three doses of MDMA were in remission from the condition two months later. The same was true for less than a quarter of the trial participants who had received only talk therapy.

At face value, these results are remarkable. Only two medications have been approved for treating PTSD in the US, both of which lead to remission in just 20 to 30 per cent of cases. But an expressed doubts about the studies at a meeting in June, ultimately voting 9 to 2 that the research had not proved MDMA’s efficacy.

One of the committee’s chief concerns was the lack of blinding, a technique that prevents participants from knowing which treatment group they are in. Approximately 90 per cent of participants receiving MDMA and 75 per cent of those given a placebo were able to accurately guess which treatment they received. This means the placebo effect could have led those in the MDMA group to expect, and thus report, an improvement in symptoms.

Another concern was the lack of details about the potential risks of MDMA. Lykos Therapeutics submitted incomplete information about the drug’s effects on the heart and also failed to collect data on its risk of abuse.

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An independent research organisation called the  also reported that it had ethical concerns about the trials. The institute found that the researchers had selected therapists, and in some cases participants, from communities that were already interested or involved in the use of psychedelics as medicine. A Lykos representative says this is untrue and that “many of the therapists had no experience with psychedelic-assisted therapy”. The report also said that the people involved in the research who had familiarity with MDMA viewed the drug “more like a religious movement than like pharmaceutical products”. According to the institute, this led some participants to feel pressured to report good outcomes on MDMA and suppress bad ones. The Lykos representative says, “Patients were encouraged to report any and all adverse events accurately over many timepoints throughout the study.”

While all of these issues probably contributed to the FDA’s rejection of the drug, they don’t spell the end of psychedelic research. For one, the FDA has asked Lykos Therapeutics to conduct another phase III trial of MDMA-assisted therapy, suggesting the agency is still open to such treatments. Researchers can also learn from this decision.

“Creating rigorous, replicable science is extremely important, and psychedelics are no exception,” says at Johns Hopkins University in Maryland. “If the advisory committee had better reasons to trust the data, we may have looked at a very different result.”

In the meantime, Lykos Therapeutics is asking the FDA to reconsider its decision. “The FDA’s request for another study is deeply disappointing,” Amy Emerson at Lykos Therapeutic said in a , noting the new research will take several years to complete. She also said that the company maintains that many of the FDA’s concerns could be addressed with existing data.

A therapy for post-traumatic stress disorder (PTSD) using the drug MDMA is likely to be approved by US regulators in the next year after the largest clinical trial to date found it was safe and effective in a diverse group of participants.

PTSD is estimated to affect of people worldwide at some point in their lives. The only pharmaceutical drugs approved to treat the condition in the US are antidepressants.

“A lot of people with PTSD are depressed and so these drugs target that depression,” says at the University of California, San Francisco. But this merely lessens the symptoms, rather than dealing with the cause of the condition, she says.

Numerous studies have investigated whether MDMA, also known as ecstasy, could be used in psychotherapy to help people with PTSD. The drug puts people into a more relaxed and trusting state and dampens fearful responses when they recall past trauma, helping them to engage more openly with therapists.

“We know that MDMA facilitates the retrieval and then the reconsolidation of fear memories within the amygdala [part of the brain that regulates emotion],” says Mitchell. “And so somehow in this process of retrieval and reconsolidation, it seems that you are shedding some of the emotionality associated with the memory.”

In June, in the world to allow doctors to prescribe MDMA for PTSD alongside psychological support.

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Mitchell and her colleagues previously showed that MDMA-assisted psychotherapy is effective, in , the majority of whom were white, with severe PTSD.

The latest study involved 104 people in the US and Israel diagnosed with moderate to severe PTSD, of whom 27 per cent identified as Hispanic or Latino and 7 per cent identified as another ethnicity or race other than white. This group is more representative of people with PTSD in the US, so the results can give more confidence that the treatment will work in a wider population, says Mitchell.

In the study, the participants all received three therapy sessions spaced a month apart. Half the group received a dose of MDMA with their therapy sessions, while the other half received a placebo pill.

Following these three therapy sessions, the researchers found that 71.2 per cent of the MDMA group no longer met the diagnostic criteria for PTSD, compared with 47.6 per cent of the placebo group.

In 2017, the US Food and Drug Administration (FDA) gave MDMA-assisted psychotherapy a . This meant that regulators worked with the research sponsors to design the clinical trials so they would deliver the evidence needed for the approval process. As a result, the treatment could receive FDA approval early next year, says Mitchell.

“These are very encouraging results which suggest that this approach may benefit PTSD,” says at King’s College London. “Although the benefits and harm should be confirmed in further research, this study brings this new treatment much closer to clinical use.”

“The latest study confirms what the previous ones have shown: that MDMA plus psychotherapy is an effective treatment for PTSD,” says at Imperial College London. “Such evidence is why the Australian government has already rescheduled MDMA for PTSD. To save lives and reduce suffering, the UK should rapidly do the same.”

Mitchell says the next question is how long the effects of MDMA-assisted therapy last. “Previous data has shown that they’re very durable and last for years, but we need to replicate that now in a phase III [advanced clinical trial] and see if that’s true, and for whom,” she says.

Dairy cows that eat leftover hemp from the cannabis industry seem high to the point of illness and have potentially unsafe levels of the psychoactive compound tetrahydrocannabinol (THC) in their milk.

More hemp is grown every year to produce plant material rich in cannabidiol (CBD) for health products. Much of the plant is thrown away, so people have suggested using it in animal feed to avoid waste. But no one knew what effect this might have if the levels of psychoactive compounds in the hemp were still relatively high.

“There is this lack of information about the health effects of cannabinoids and the putative transfer into food of animal origin,” says at the German Federal Institute for Risk Assessment.

Pieper and his colleagues measured this transfer by feeding five cows a hemp mixture naturally low in cannabinoids for six days and another five a mix that had high levels.

When they measured the milk from the high-concentration group using mass spectroscopy, they found high levels of several cannabinoids, including delta-9-THC, one of the most abundant psychoactive compounds in cannabis. If a normal amount of this milk was drunk by someone, they would receive a dose of THC where there could be “appreciable health risks” according to , says Pieper.

“This is important, as we had no data to know to what extent cannabinoids entered the milk of dairy cows,” says at Kansas State University College of Veterinary Medicine. While conclusions can’t be drawn from the data itself, it will be useful for government agencies looking to see whether hemp can be used as animal feed, he says.

Pieper and his team also found that the cows acted markedly different when fed with the high-concentration feed, yawning, appearing sleepy and standing for unusually long periods in the same posture, as well as having abnormally slow breathing and heart rates – effects that are typically only seen in the course of serious illnesses.

It is unclear which elements of the industrial hemp were causing these behavioural changes, says Pieper, because the hemp contained many different cannabinoids.

He doesn’t think the term “high” should be used for the cows, though, because it describes a whole series of physiological and psychological changes in humans and we don’t know what the cows are feeling. Some observations, such as sleepiness, could also be attributed to the effect of CBD, he says.