Participants in a traditional Ayahuasca ritual of spiritual and physical healing in La Calera, Cundinamarca, Colombia in 2014. Photo by Eitan Abramovich/AFP/Getty
Psychedelics have a remarkable capacity to violate our ideas about ourselves. Is that why they make people better?
Psychedelic drugs are making a psychiatric comeback. After a lull of half a century, researchers are once again investigating the therapeutic benefits of psilocybin (‘magic mushrooms’) and LSD. It turns out that the hippies were on to something. There’s mounting evidence that psychedelic experiences can be genuinely transformative, especially for people suffering from intractable anxiety, depression and addiction. ‘It is simply unprecedented in psychiatry that a single dose of a medicine produces these kinds of dramatic and enduring results,’ Stephen Ross, the clinical director of the NYU Langone Center of Excellence on Addiction, told Scientific American in 2016.
Just what do these drugs do? Psychedelics reliably induce an altered state of consciousness known as ‘ego dissolution’. The term was invented, well before the tools of contemporary neuroscience became available, to describe sensations of self-transcendence: a feeling in which the mind is put in touch more directly and intensely with the world, producing a profound sense of connection and boundlessness.
How does all this help those with long-term psychiatric disorders? The truth is that no one quite knows how psychedelic therapy works. Some point to a lack of knowledge about the brain, but this is a half-truth. We actually know quite a lot about the neurochemistry of psychedelics. These drugs bind to a specific type of serotonin receptor in the brain (the 5-HT2A receptor), which precipitates a complex cascade of electrochemical signalling. What we don’t really understand, though, is the more complex relationship between the brain, the self and its world. Where does the subjective experience of being a person come from, and how is it related to the brute matter that we’re made of?
It’s here that we encounter a last frontier, metaphysically and medically. Some think the self is a real entity or phenomenon, implemented in neural processes, whose nature is gradually being revealed to us. Others say that cognitive science confirms the arguments of philosophers East and West that the self does not exist. The good news is that the mysteries of psychedelic therapy might be a hidden opportunity to finally start unravelling the controversy.
The nature of the self has been disputed for as long as people have reflected on their existence. Recent neuroscientific theories of selfhood are recognisably descended from venerable philosophical positions. For example, René Descartes argued that the self was an immaterial soul whose vicissitudes we encounter as thoughts and sensations. He thought the existence of this enduring self was the only certainty delivered by our (otherwise untrustworthy) experience.
Few neuroscientists still believe in an immaterial soul. Yet many follow Descartes in claiming that conscious experience involves awareness of a ‘thinking thing’: the self. There is an emerging consensus that such self-awareness is actually a form of bodily awareness, produced (at least in part) by interoception, our ability to monitor and detect autonomic and visceral processes. For example, the feeling of an elevated heart rate can provide information to the embodied organism that it is in a dangerous or difficult situation.
David Hume disagreed with Descartes. When he attended closely to his own subjectivity, he claimed to find not a self, but a mere stream of experiences. We incorrectly infer the existence of an underlying entity from this flow of experiential moments, Hume said. The modern version of this view is that we have perceptual, cognitive, sensory and, yes, bodily experiences – but that is all. There’s an almost irresistible temptation to attribute all this to an underlying self. But this substantialist interpretation is a Cartesian mistake, according to Hume…