Psilocybin microdosing fails to boost cognitive performance in rigorous trials

A popular modern trend involves taking tiny amounts of psychedelic mushrooms to boost brain power, but new evidence suggests the benefits may be largely imaginary. A rigorous scientific investigation found that consuming small amounts of psilocybin offered no measurable improvements in cognitive function or mood compared to a dummy pill. These results come from a comprehensive report published in the journal Neuropharmacology. The findings challenge the growing industry built around the alleged benefits of sub-perceptual psychedelic use.

The practice is known as microdosing. It typically involves ingesting about one-tenth to one-twentieth of a standard recreational dose of a psychedelic substance. Users aim to sharpen their minds or brighten their moods without experiencing the hallucinations or disorientation associated with a full trip. Proponents and media reports often claim this regimen enhances creativity, focus, and general productivity.

However, much of the existing praise for microdosing comes from personal stories rather than strict science. Past research often failed to account for the placebo effect. This occurs when people feel better simply because they expect a treatment to work. Without a control group, it is impossible to separate chemical effects from psychological expectations. Observational studies have reported benefits ranging from better social skills to reduced anxiety. Yet these studies relied on participants who knew they were taking a drug.

Luisa Prochazkova of Leiden University led a team to investigate these claims using a more skeptical approach. They designed their experiment around a concept known as the metacontrol state model. This psychological theory suggests the human brain balances two modes of processing. One mode is persistence, which allows a person to stay focused on a specific goal and ignore distractions. This is often called proactive control.

The other mode is flexibility. This mode helps a person switch tasks, adapt to new information, or think outside the box. Theoretical models suggest that pharmacological interventions often force a trade-off between these two styles. For example, a drug that improves focus might make a person less flexible. The researchers hypothesized that psilocybin might shift the brain toward flexibility. They suspected this shift might come at the cost of reduced focus. To test this, they needed to see if the drug changed how people solved specific types of problems.

The investigation consisted of two separate experiments conducted in the Netherlands. The researchers used psilocybin-containing truffles for the active doses. They recruited healthy volunteers who were screened for mental health issues. The study used a design considered the gold standard in medical research. This design is called a randomized, double-blind, placebo-controlled trial.

Participants were randomly assigned to receive either the truffles or a harmless placebo. Neither the volunteers nor the researchers knew who received which pill until the study ended. This precaution prevented expectations from influencing the results. The researchers employed a longitudinal approach, meaning they tracked the participants over several weeks rather than just looking at a single day.

In the first experiment, participants consumed about 0.65 grams of fresh truffles. They followed a schedule of taking a dose every few days for roughly four weeks. During this time, they completed a battery of computer tests. These tests measured memory, the ability to ignore distractions, and social insight. One of the primary tools used was the AX-Continuous Performance Task.

This task measures the balance between maintaining a goal and reacting to new inputs. A participant sees a sequence of letters and must press a button only when a specific pair appears. It requires sustained attention. The researchers also used a “multi-armed bandit” task. This game tests whether a person prefers to stick with a known reward or explore new options. This helps measure the trade-off between exploitation and exploration.

The results from the first experiment revealed no consistent differences between the two groups. The microdosing group did not perform better on memory tasks. They showed no advantage in their ability to focus or switch between tasks. The researchers observed a slight improvement in recognizing emotions in the microdosing group during a social cognition test. However, this finding was not statistically significant after adjusting for the number of tests run. It was likely a random fluctuation in the data.

To ensure the dose was strong enough to elicit a response, the team conducted a second experiment. They increased the truffle amount to one gram per dose. They also extended the total duration of the study to eight weeks. This second trial introduced different cognitive challenges to cast a wider net. The team wanted to ensure they were not missing effects simply because they chose the wrong tasks.

One challenge in the second experiment measured working memory using a task called the N-back. This requires a participant to remember a letter presented several steps earlier in a sequence. It is a demanding test of mental holding power. Another task assessed visual attention capabilities through an “attentional blink” test. This measures the ability to notice a second target image that appears rapidly after a first one.

The researchers also included games designed to measure trust and social closeness. One such game involved exchanging money with a virtual partner to test interpersonal trust. Once again, the data showed that the drug did not outperform the placebo. Both groups reported feeling more trusting and closer to others over time. This suggests that the passage of time or the study environment caused the change. The chemical content of the truffles was not the cause.

Self-reported questionnaires about mood and mindfulness yielded similar results across both experiments. Participants in the psilocybin group did not report higher levels of well-being than those taking the placebo. They did not show greater increases in psychological flexibility. The team checked to see if the blinding procedure was successful. They asked participants to guess whether they had taken the active drug or the placebo.

The volunteers could not guess their group assignment better than chance. This confirms that the doses were small enough to avoid obvious psychedelic effects. It also validates the comparison between the groups. If participants had known they were medicated, their expectations might have skewed the data. The study also analyzed open-ended text reports from the participants.

Even in these qualitative reports, the benefits were not evident. Participants in the placebo group were just as likely to report positive emotional changes as those in the active group. This strongly implies that the “microdosing glow” often reported in anecdotal accounts is driven by the placebo effect. People expect to feel better, so they do.

There was one area where the groups differed. Participants taking the real truffles reported more negative physical sensations. These included feelings of nausea, temperature changes, or general bodily discomfort. The placebo group experienced these physical symptoms less frequently. This suggests the drug was pharmacologically active in the body, even if it did not change the mind. The most consistent effect of the drug was a slight increase in negative bodily awareness.

These findings present a challenge to the popular narrative around microdosing. However, the study does have limitations. The experiments took place in a controlled laboratory setting. Standardized computer tests might not capture subtle changes in creativity or insight. It is possible that the benefits of microdosing are not apparent in rigid tasks.

Real-world scenarios might reveal effects that laboratory tests miss. Additionally, the participants were healthy individuals. A person functioning at a high level may have little room for improvement. This is often referred to as a ceiling effect. A drug might help someone with a deficit return to normal, but it might not make a healthy person “better than normal.”

Future research could focus on different populations. People suffering from depression or anxiety might respond differently than healthy volunteers. The researchers suggest that future studies should examine whether specific groups benefit more than others. They also recommend using more naturalistic assessments to measure daily functioning. For now, the scientific evidence suggests that for healthy people, microdosing psilocybin is unlikely to provide the cognitive boost that users seek.

The study, “Cognitive and subjective effects of psilocybin microdosing: Results from two double-blind placebo-controlled longitudinal trials,” was authored by Luisa Prochazkova, Josephine Marschall, Dominique Patrick Lippelt, Neil R. Schon, Martin Kuchař, and Bernhard Hommel.