Researchers have shown that magic mushrooms reduce symptoms of depression weeks after treatment following a 'reset' of brain activity.
Robin Carhart-Harris and his team at Imperial College London have been testing psilocybin -- a hallucinogen found in magic mushrooms -- in people with treatment-resistant depression. Their pilot study found that when it was given to 12 volunteers alongside psychological support, five of them no longer met the clinical criteria for a depression diagnosis three months later.
But how can you tell if psilocybin might help someone? Working with the Imperial team, Facundo Carrillo at the University of Buenos Aires in Argentina and his colleagues tested the idea that speech patterns give a clue.
Speech analysis has already been used to identify people with a range of mental health disorders, including depression and schizophrenia. "Language is a window to the mind," says Matthew Johnson at Johns Hopkins University in Baltimore, Maryland. "It's a huge part of how people express themselves."
Carrillo's team developed software to analyse interview responses given by 17 people with treatment-resistant depression before psilocybin treatment, and 18 people without depression.
The psilocybin treatment seemed to reduce the symptoms of seven of the people with depression by more than 50 per cent. Using the results to train their software, the researchers say it can predict whether a person with depression will respond to psilocybin with 85 per cent accuracy
They found that people with depression use significantly fewer positive words than those without the condition. Those with depression who are likely to respond to treatment use fewer positive words than those who aren't.
This is a promising way to screen people, says Gabrielle Agin-Liebes at Palo Alto University in California. "It is a very intense treatment, so being able to screen for people who we think are the best matches would be a real asset."
She stresses that the tool, if shown to work in larger groups, should be used to aid doctors rather than replace them.
While 85 per cent prediction power is far from ideal, it's better than what we have for existing treatments for depression, says Johnson. "Nearly every treatment in psychiatry will work for some people but not others," he says. "Any level of prediction is helpful."
Psilocybin is still a way off being rolled out for clinical use -- only a handful of studies have been conducted so far, and larger trials are needed to confirm that it is safe and effective.
But Johnson is optimistic that psilocybin could be useful for some people with depression. "It's unprecedented to be able to give a single dose of medication and to have a large decrease in depressive symptoms months later," he says. "It's not ready for prime time, but the results so far are very promising."