Placebo Effect vector illustration blue.

Is Microdosing Just Placebo?

By Vince Polito

People who microdose psychedelics claim that it provides a very wide range of benefits, from improvements in mood, to reduced substance use, to cognitive enhancement.

But is microdosing really delivering all of those benefits? Or is it just a placebo effect?

On the one hand, developing evidence from studies with psychedelics taken at high doses does indicate that these substances may plausibly have a range of positive effects. But, at the same time, the claimed benefits seem potentially outsized relative to the doses involved in microdosing, which typically involves 1/10th to 1/20th of a recreational or clinical dose. Further, the positive media and internet narrative around microdosing seems likely to generate strong positive expectations that may influence users’ reports.

With these factors in mind, fellow psychologist Paul Liknaitzky and I recently completed a comprehensive systematic review of all research with low doses of psychedelic substances, in order to summarize what we know about the likely effects of microdosing.

We identified 44 relevant studies from the 1950s through to mid-2021. These were a mix of qualitative studies (e.g., interviews with microdosers); self-report surveys (questionnaires administered to people who microdose); prospective observational studies (studies that tracked the experiences of microdosers in a naturalistic setting over multiple timepoints); and laboratory studies (studies that investigated the effects of microdoses administered in a controlled setting).

We found that study quality varied considerably and that, overall, self-report studies found a wider range of benefits than controlled laboratory studies. We did however, identify several effects that were reported consistently across both laboratory and self-report studies. The clearest evidence was for changes in time perception, increased pain tolerance, and mild alterations in conscious state.

We also identified several variables that showed up consistently in self-report studies but that have not yet been well investigated in a laboratory environment. These included improvements in mental health, changes in attentional capacities, such as absorption and mind wandering, personality changes, and wellbeing (see table below for full list). These are all promising targets for well-controlled future research.

Finally, we identified several variables that appeared promising according to self-report studies, but that were tested and not confirmed in lab studies. These include improved mood, changes in social and general cognition, and increased energy. It may be that these variables are unaffected by microdosing. However, one complicating factor that is relevant to interpreting these results is that the lab studies included in this review investigated the acute effects of a single dose or a small number of doses, whereas the self-report studies typically reported on enduring changes following a longer course of microdosing. For this reason, it is hard to be confident about interpreting these null findings.

It is also worth noting that there is uncertainty around exactly what doses should be considered microdoses. Many microdosing guides suggest that these doses should be sub-perceptual – in other words, so low that users don’t notice any changes in their conscious state. But self-reported data from microdosers indicates that their practice does lead to very mild alterations in consciousness.

Table 1: Current evidence for microdosing effects.

Effects found in both self-report and lab studies Effects found in self-report studies but not well investigated in lab studies Effects found in self-report studies; investigated but not confirmed in lab studies
  • Altered time perception
  • Pain tolerance
  • Changes in conscious state
  • Improved mental health
  • Reduced substance use
  • Increased absorption
  • Reduced mind wandering
  • Personality changes
  • Insight
  • Nature relatedness
  • Wellbeing
  • Improved mood
  • Social connection
  • Improved cognition
  • Enhanced emotional processing
  • Increased energy

New developments

Things are moving fast in microdosing science.

Since completing our formal review, there have been at least another seven studies of microdosing. Six of these have been well-designed, lab-based studies with controlled dosing. Overall, these very recent studies have not identified strong effects related to microdosing. In fact, in several studies, participants’ guess about what substance they had taken (microdose or placebo) had a stronger influence on outcomes than the substance itself. These findings have led some researchers and commentators to argue that microdosing may be predominately a placebo effect. This may turn out to be the case. Microdosers’ expectations clearly have some influence on the outcomes that are reported.

However, I suggest that it is premature to rule out a pharmacological effect of microdosing for two reasons.

First, lab studies so far have only looked at the short-term effects of microdosing (the longest involved 7 doses). It may be that benefits of microdosing emerge only after a longer dosing schedule.

Second, there has not yet been any clinical trial of microdosing. All lab-based studies to date have investigated healthy populations. It may be that there are clinical benefits that are specific to particular conditions.

Microdosers regularly report considerable positive impacts from microdosing. As a striking example, in one study, more than 50% of respondents reported ceasing traditional medications after they started microdosing. To conclusively understand what might be driving such effects, we need well-controlled, longitudinal studies targeting clinical populations.

Vince Polito is a Senior Research Fellow in the School of Psychological Sciences, and member of the Biomolecular Discovery Research Centre at Macquarie University.

The Petrie-Flom Center Staff

The Petrie-Flom Center staff often posts updates, announcements, and guests posts on behalf of others.

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