The psychedelic drug psilocybin could help alleviate depression by causing people to have a less pessimistic outlook on life, according to preliminary research published in Frontiers in Psychology.

Previous research has found that depression is associated with unrealistic negative predictions of future life events. Scientists from the Psychedelic Research Group at Imperial College London were interested in whether psilocybin — the main psychoactive compound in magic mushrooms — could reduce these pessimism biases.

In their study, 15 participants with treatment-resistant depression were administered psilocybin in two dosing sessions. Psychological support was provided before, during, and after each session.

The participants — along with group of matched, untreated non-depressed controls — completed measures of depression and predictions of future life events before and after the psilocybin sessions.

Before the treatment, the depressed participants predicted they would experience an roughly equal number of undesirable events and desirable events in the future. The non-depressed participants, on the other hand, predicted they would experience more desirable events than undesirable events.

But treatment with psilocybin appeared to alter the depressed participants’ predictions of future life events. After the psilocybin sessions, depressed participants expected more desirable than undesirable life events to occur, which was in turn associated with a reduction in depressive symptoms.

“Before treatment with psilocybin, patients were excessively and unrealistically pessimistic when predicting the occurrence of future life events — and this pessimism was significantly correlated with the severity of their depressive symptoms. One week after treatment, the patients’ pessimism was alleviated and their depressive symptoms greatly improved; moreover, the magnitude of change in both variables was related – such that as their depression improved, so did their ability to accurately forecast their future,” the researchers explained.

“No such bias nor change in forecasting was seen in a matched control group assessed over an equivalent time period. Taken together, these findings indicate that the psychologically supportive administration of psilocybin remediates negative cognitive biases characteristic of severe depression – enabling individuals to forecast their futures more accurately, unfettered by unrealistic pessimism.”

The findings are promising, but need to be replicated with a larger sample of participants, the researchers noted.

The study, “More Realistic Forecasting of Future Life Events After Psilocybin for Treatment-Resistant Depression“, was authored by Taylor Lyons and Robin Lester Carhart-Harris.