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If you’ve ever been to London, you know that navigating its wobbly grid, full of curves and dead-end streets, requires an impressive spatial memory. Driving around London is so challenging, in fact, that researchers in 2006 found it was linked to changes in the brains of taxi drivers in the city: compared to Londoners driving fixed routes, taxi drivers had more gray matter volume in a century. The amonium, a brain region critical to the formation of spatial memory. The longer the cab driver, the greater the effect.
The study is particularly evocative evidence of neuroplasticity: the human brain’s innate ability to change in response to environmental input (in this case, the challenging spatial task of driving a taxi around London). Hard-won neuroplasticity requires years of mental and physical practice. Wouldn’t it be nice to get the same effects without much effort?
To hear some people say it, you can: psychedelic drugs such as psilocybin, LSD, ayahuasca, and Ecstasy, along with anesthetics such as ketamine, can enhance a user’s neuroplasticity within hours of ingestion. In fact, some users take the drug for the express purpose of making their minds more flexible. Just drop some acid, the thinking goes, and your brain will rewire itself—you’ll be smarter, fitter, more creative, and more self-aware. You might even get a super experience. Popular media abounds with anecdotes suggesting that even small doses of LSD or psilocybin can expand divergent thinking, the freer, more associative type of thinking that some psychologists associate with creativity.
Research suggests that psychedelic-induced neuroplasticity can actually enhance certain types of learning, particularly in terms of overcoming fear and anxiety associated with past trauma. But claims about the drug’s transformative and brain-enhancing effects are, for the most part, exaggerated. We don’t really know yet how much small doses, or the full journey, will change the average person’s mental circuits. There is reason to suspect that such changes may be actively harmful to some people.
There is nothing new about the idea that the human and animal brain is voluntary in response to everyday experience and injury. It is said that the philosopher and psychologist William James first used the term ductility in 1890 to describe changes in the neural pathways involved in the formation of habits. We now understand that these changes occur not only between neurons but also within them: individual cells are able to germinate new connections and reorganize in response to all kinds of experiences. Essentially, this is a neural response to learning, which the drug can elevate.
We also understand how effective psychedelic drugs can cause changes in the brain. Injecting psilocybin into a mouse can stimulate neurons in the frontal cortex to grow by about 10 percent and sprout new spines, projections that reinforce connections with other neurons. It also moderated their stress-related behaviors—effects that persisted for more than a month, suggesting continued structural change associated with learning. A similar effect should occur in humans. (Comparative studies in humans would be impossible, because investigating changes in a single neuron would require, well, sacrificing the subject.)
The thing is, not all of these changes are necessarily all of them good. Neuroplasticity just means that your mind – and your mind – is put into a state where it is easier to influence. The effect is a bit like putting a glass vessel back in the kiln, which makes it pliable and easy to reshape. Of course, you can make the vase more practical and beautiful, but you can also turn it into a mess. Above all, psychedelic substances make us wonderfully aroused, thanks to the speed of their action and the magnitude of their effect, although their final effect is still very dependent on context and effect.
We’ve all experienced an increase in neuroplasticity during the so-called sensitive periods of brain development, which usually unfold between ages 1 and 4 when the brain uniquely responds to environmental input. This helps explain why children learn all kinds of things so effortlessly, like how to skate or speak a new language. But even in childhood, you do not acquire your knowledge and skills in magic; you have to Do Something in the environment is stimulating enough to take advantage of this nervous state. If you have the misfortune of being neglected or abused during your brain’s sensitive periods, the effects are likely to be harmful and persistent—perhaps more so than if the same events occurred later in life.
Being in a neuroplastic state enhances our ability to learn, but it can also burn through negative or traumatic experiences — or memories — if you come across them while on a psychedelic drug. Last year, a patient of mine, a woman in her early 50s, decided to try psilocybin with a friend. The experience is very interesting until she begins to recall memories of her emotionally abusive father, who was an alcoholic. In the weeks following her psilocybin exposure, she has vivid and distressing memories of her childhood, which sends her into severe depression.
Her experience might have been very different—and perhaps even positive—if a mentor or therapist had been with her during her stumble to help her reevaluate these memories and make them less toxic. But without the positive effect of mediation, she is left to the mercy of her own imagination. That must have been just the kind of situation Oregon lawmakers had in mind last month when they legalized recreational psilocybin use, but only in conjunction with a licensed guide. It’s the right idea.
In fact, researchers and clinicians have no evidence as to whether people who frequently take small doses with narcotic medications — and thus wander into a state of enhanced neuroplasticity — are more likely to encode traumatic events. In order to find out, you would have to compare a group of people who took microdoses to a group of people who didn’t over a period of time, and see if they differed in rates of PTSD, for example. Crucially, you’ll have to randomly assign people to either the mini-dose or to abstain – not just let them choose whether they want to experience tripping. In the absence of such a study, we are all currently participating in a large, uncontrolled social experiment. The results will inevitably be messy and inconclusive.
Even if opening your brain to change is a good thing, the promise of infinite neuroplasticity—that you can rejuvenate and reshape the brain at any age—far outstrips scientific evidence. Despite claims to the contrary, each of us has an upper limit on how flexible our brains can be. Sensitive periods, when we reach our maximum plasticity, are a limited window of opportunity that closes as the brain matures. We gradually lose neuroplasticity as we age. Of course we can keep learning – it takes more effort than when we were young. Part of this change is structural: At age 75, the hippocampus has fewer neurons connected to each other than it did at age 25. This is one of the main reasons older people find their memory isn’t as sharp as it used to be. You can improve those connections a bit with a dose of psilocybin, but you can’t simply make your brain act like it’s five decades younger.
This reality has never stopped a highly profitable industry from fulfilling the fears and hopes of people – especially the elderly. You don’t have to search the internet for long before you find all kinds of nutritional supplements that claim to keep your brain young and sharp. Brain training programs go further, claiming to rewire your brain and enhance your cognition (sound familiar?), when in reality the benefits are very modest and limited to whatever cognitive task you’ve ever taken on. Memorizing a string of numbers will make you better at memorizing numbers; It won’t transfer to another skill and make you better at chess, for example.
We lose neuroplasticity as we age, and for good reason. To retain our experience, we don’t want our brain to rewire itself too often. Yes, we lose cognitive fluidity along the way, but we also gain knowledge. This isn’t a bad trade-off. After all, it is probably more valuable for an adult to be able to use all his accumulated knowledge than to be able to solve a new mathematical problem or learn a new skill. More importantly, our identity itself is encoded in our neural architecture—something we don’t want to mess with lightly.
At their best, narcotics and other neuroplasticity-enhancing drugs can do some pretty remarkable things, like speed up the treatment of depression, calm anxiety in terminally ill patients, and ease the worst symptoms of PTSD. This is reason enough to research its uses and inform patients that psychedelics is an option for psychotherapy when supported by evidence. But drug-induced self-improvement is an illusion.