“Humans have been using magic mushrooms for thousands of years, and indigenous societies have long used them in rituals,” says Bruna Giribaldi, clinical trial manager at the Centres for Psychedelic Research and Neuropsychopharmacology at Imperial College London.

Speaking at an online conference organised by New Scientist Live, an offshoot of the UK’s New Scientist magazine, Giribaldi noted that psilocybin has the power to help patients relive traumatic experiences that have been repressed. It can also make depressed users feel better about themselves.

“It’s important to highlight that psychedelics don’t just make people see things, they make people feel things in a different way. They allow people to have profound feelings of love and compassion for themselves and others, which can be incredible.

“Such feelings can also help them to feel deeply connected to themselves and others. People can feel pleasure and have spiritual experiences,” she said.

Once ingested, psilocybin is rapidly metabolised to psilocin, which acts on serotonin receptors in the brain. Serotonin is a neurotransmitter, one of the chemicals that the brain uses to communicate with itself. (One of the many things serotonin does is improve mood.)

Serotonin binds to many kinds of receptors to send messages around the brain, and psilocybin affects its relationship with a specific receptor known as 5-HT2A. The more psilocybin you give a patient, the more 5-HT2A receptors serotonin binds to.

What happens next is the interesting part. Such bindings do happen naturally, but with psilocybin, many, many more connections are made. The brain effectively rewires itself by adding a lot more “wires”, and these new connections enable the different areas of the brain to work together in a different way.

Those who have read about LSD experiences will have heard of the idea of colours having a sound attached to them, for instance. When psychedelic drug users talk about the fridge singing to them, this is what is going on in their brains.

“Psilocybin makes areas of the brain that don’t usually connect with each other start connecting, and that means, for instance, your visual field can connect with your emotions,” said Giribaldi.

Many parts of the brain start communicating with many other parts, so our view of the outside world – which is formed by the way the brain interprets the perceptions it receives from our senses – changes as a result.

So how do these changes help depressed people?

“The theory is that psychedelics relax the strong beliefs that people have about the world,” Giribaldi said. “By relaxing your beliefs, you are able to see things in a different way.

“This is useful in mental illness, because the one thing that unites all mental illnesses like depression and addiction is a strong and rigid set of thinking, or a strong set of ideas about what is happening in the world.”

With the therapy that acts alongside the psilocybin, patients are able to think differently, and hopefully see the world more positively.

“Your brain usually sees things in a particular way, and that can be relaxed under psychedelics and possibly revised in a safe context to allow yourself to see the world in a different way,” said Giribaldi. Research has shown that the positive effects last much longer than those gained from drugs like Prozac, she added.

Although psychedelic drugs are not addictive, psilocybin needs to be administered in a controlled medical setting, she stressed.

After taking psilocybin, “you are very vulnerable to outside stimuli which can change your brain. It could be a very good direction of change, but if you are in a bad context you could be traumatised. That is why context is important.

“We have safe environments and trained people to make sure that it is safe so we can change people’s lives for the better in a very powerful way.”

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