Microdosing psychedelics is the practice of consuming very low, sub-hallucinogenic doses of a psychedelic substance, such as lysergic acid diethylamide (LSD) or psilocybin-containing mushrooms. According to media reports, microdosing has grown in popularity, yet the scientific literature contains minimal research on this practice. There has been limited reporting on adverse events associated with microdosing, and the experiences of microdosers in community samples have not been categorized.
In the present study, we develop a codebook of microdosing benefits and challenges (MDBC) based on the qualitative reports of a real-world sample of 278 microdosers.
We describe novel findings, both in terms of beneficial outcomes, such as improved mood (26.6%) and focus (14.8%), and in terms of challenging outcomes, such as physiological discomfort (18.0%) and increased anxiety (6.7%). We also show parallels between benefits and drawbacks and discuss the implications of these results. We probe for substance-dependent differences, finding that psilocybin-only users report the benefits of microdosing were more important than other users report.
These mixed-methods results help summarize and frame the experiences reported by an active microdosing community as high-potential avenues for future scientific research. The MDBC taxonomy reported here informs future research, leveraging participant reports to distil the highest-potential intervention targets so research funding can be efficiently allocated. Microdosing research complements the full-dose literature as clinical treatments are developed and neuropharmacological mechanisms are sought. This framework aims to inform researchers and clinicians as experimental microdosing research begins in earnest in the years to come.
Introduction Psychedelic mushrooms
The practice of microdosing psychedelics involves ingesting sub-hallucinogenic amounts of a psychedelic substance (e.g. LSD, psilocybin) and has recently grown in popularity. The number of popular media accounts and book-length treatments of microdosing has been growing [1,2,3,4,5,6,7]. Online microdosing communities have grown to the tens of thousands with more than 40,000 users subscribing to the /r/microdosing subreddit (/r/microdosing subreddit, Reddit Inc, San Francisco, CA, USA). This public interest speaks to a social need for scientific studies to inform the public about the effects of microdosing. Initial scientific investigations of microdosing are just beginning [8,9,10,11] (Rosenbaum D, Weissman C, Hapke E, Hui K, Petranker R, Dinh-Williams L-A, et al.: Microdosing psychedelic substances: demographics, psychiatric comorbidities, and comorbid substance use, in preparation) and future directions remain unclear. While full-dose psychedelic research is growing in prominence and outcomes from full-dose studies can certainly inform microdosing studies, focusing solely on known full-dose outcomes could result in missing unanticipated benefits and challenges specific to microdosing. As such, beginning with an open, exploratory approach could result in a better understanding of the potential benefits and challenges specific to microdosing. The present study aims to provide a data-driven taxonomy describing the positive and negative experiences reported by microdosers from an open-ended analysis of microdosing-specific outcomes, summarizing high-potential avenues for focused experimental investigations.
The benefits of full-dose psychedelics
While more than a thousand early studies linked psychedelic use with beneficial effects , there was a 40-year pause on psychedelic research following the prohibition of these substances . Despite continued prohibition, modern research has revealed the promising potential of LSD and psilocybin for treating alcohol and tobacco dependence [14,15,16,17], depression [18, 19], and end-of-life anxiety [20,21,22], while related research on 3,4-methylenedioxymethamphetamine (MDMA) has shown great promise for treating post-traumatic stress disorder . Psychedelics can also increase openness and occasion mystical-type experiences in healthy controls [24,25,26]. As full-dose psychedelics appear to aide in the relief of severe, chronic psychiatric conditions (e.g. depression, anxiety, PTSD), milder mental health concerns may plausibly be treated by lower, recurring doses. This is especially worth considering if certain full-dose outcomes are found to rely on purely pharmacologic mechanisms rather than primarily on phenomenological experiences .
Limiting microdosing research to topics that have been investigated in full-dose research could prematurely overlook unpredicted and potentially distinct microdosing outcomes. Full-dose research has employed various focal assessments of symptomatology, mood, and personality that are likely applicable to microdosing research, but due to the low doses and lack of perceptual alteration intended in microdosing, other full-dose phenomena, such as ego dissolution and mystical-type experiences, are less relevant to microdosing research. Instead, as a means of preparing for a broad range of outcomes, the present work solicited open-ended reports of benefits and challenges. Additionally, as psychedelic substances act on distinct yet overlapping neural receptor sites, it seems plausible that distinct patterns could emerge for different substances. The present study thus included microdosers who used LSD, psilocybin, or both.
The challenges of full-dose psychedelics
While psychedelics appear to have considerable potential benefits and low physiological risks [28,29,30], full-dose experiences can put participants under considerable psychological risk . In a survey targeting participants that had at least one challenging experience (“bad trip”) with psilocybin mushrooms, 39% of respondents rated their full-dose experiences as among the top 5 most psychologically difficult/challenging experiences of their lives . Griffiths et al.  used both “high” (22 mg/70 kg) and “low” (1 or 3 mg/70 kg) doses of psilocybin as experimental and control conditions, respectively. A dose-response effect could be seen such that in the high-dose condition, 32% of participants reported physiological discomfort whereas only 12% reported the same in the low-dose condition; likewise, 26% reported anxiety in the high-dose condition versus 15% in the low-dose condition . Delayed-onset headaches are another possible side-effect of full-dose psilocybin .
To mitigate these risks, Johnson et al.  proposed safety guidelines for use with full-dose psychedelic substances, which rely on managing participant inclusion and having a comfortable, guided clinical setting. As microdosing does not involve the intensity of experience present in full-dose research, challenging experiences may be less likely. One may, however, anticipate that less frequent, less intense versions of full-dose challenges could be present even at the very low doses used in microdosing (e.g. restlessness instead of insomnia, mild anxiety instead of fear, mild headaches). As the study of microdosing is in its infancy, we could also expect there to be challenges that fall beyond the scope of reports based on full doses; the present study thus preferred open-ended surveying of drawbacks over pre-existing focal questionnaires.
The present study
In this study, we explored the benefits and challenges experienced by microdosers in a cross-sectional, retrospective, anonymous online survey. Respondents reported their subjective microdosing benefits and challenges (MDBCs) and the subjective importance of each outcome. We then used a grounded theory approach  to identify commonly-reported MDBCs and thereby deliver an empirical MDBC taxonomy to support future microdosing research. We also explored whether microdosing substances (LSD-only versus psilocybin-only versus LSD and psilocybin) were associated with different outcomes.
This study was part of a larger project that reported on the demographic and psychiatric comorbidities of the sample (Rosenbaum D, Weissman C, Hapke E, Hui K, Petranker R, Dinh-Williams L-A, et al.: Microdosing psychedelic substances: demographics, psychiatric comorbidities, and comorbid substance use, in preparation) as well as a paper that addressed pre-registered hypotheses concerning mental health, personality, and creativity variables .
Grounded theory method
Microdosers were prompted to provide up to three benefits and up to three challenges associated with microdosing in small on-screen text boxes, resulting in short phrases (e.g. “Amplified emotions and better understanding of them”, “Fear of unknown effects, since its [sic] not studied”) or in one- or two-word responses (e.g. “Creativity”, “Better mood”, “Illegal”, “Too Energetic”). The coding authors (TA and AC) independently coded these benefits and challenges using the principles of classic grounded theory [34,35,36]. Discrepant codes were periodically discussed until a final set of codes was agreed upon (i.e. saturation was reached). These codes were hierarchically built into three layers of abstraction: codes (level one) were grouped under sub-categories (level two), which were grouped under categories (level three). This hierarchy was iteratively discussed and changes were agreed upon over five refining passes. We incorporated the diction used by the respondents where possible to better reflect the data-driven nature of the final codebook (see Additional file 1 and full online codebook; ).
Inter-rater agreement was calculated separately for benefits and challenges and at each level (code, sub-category, category). Agreement was above 85% at every level (benefit code 85.1%, benefit sub-category 89.2%, benefit category 92.6%; challenge code 85.7%, challenge sub-category 86.9%, challenge category 88.5%). Each report was coded twice, once by each coding author, and the sum of coded items in each category was halved; as a result, the frequency of any given category can be a non-integer value (e.g. 807.5 coded benefits, 603.5 coded challenges; “Empirical codebook: benefits of microdosing” and “Empirical codebook: challenges of microdosing” sections).