This is Part 1 in a two-part series about the lack of representation in psychedelic research. This first part explores the history of medical bias that continues to systematically exclude women, minorities, and gender diverse people from clinical trials. Part 2 explores the structural issues within the medical model and imagines community-based alternatives.
Recent years have seen a global explosion in psychedelic research and treatment development, coupled with unexpected wins such as President Trump’s executive order to expedite the research and review of psychedelic drugs for therapeutic use in April 2026.
A growing body of research shows that psychedelics have an immense potential when it comes to therapeutic treatment, especially for mental health disorders. However, the current direction in which psychedelic R&D is heading leaves us with an important dilemma: with such a highly medicalised model, how can such a groundbreaking transformation happen when key populations who need this treatment most continue to be systematically excluded from clinical trials?
This was the focus of this year’s International Conference of Psychedelic Research (ICPR 2026). Focusing on the history of bias in biomedical research, and more specifically on the systematic omission of gender differences in clinical trials, Grace Blest-Hopley – founder of Hystelica, a psychedelic research organisation focusing on the use of psychedelics to understand, treat, and empower women’s health – brought this topic to light in her impactful opening keynote speech titled, “The 51% Blind Spot: Psychedelics, women’s health, and the opportunity we must not miss”.
Repeating past mistakes
The issue of women’s systemic exclusion from biomedical research is not new. It wasn’t until 1993 that women and minorities were required to be included in clinical research funded by the National Institute of Health in the US (and 2014 when the European Medicines Agency introduced the EU Clinical Trial Regulation No. 536/2014).
The consequences of this decades-long omission are still being felt. Many medications prescribed today were approved by the FDA before this requirement existed, meaning they were tested primarily on white, male bodies and then generalised to all populations. The fact that women experience adverse drug reactions nearly twice as often as men is largely a direct legacy of this history.
Women are disproportionately affected by the very conditions psychedelic-assisted therapy shows the most promise in addressing. Depression affects women at roughly twice the rate of men. Anxiety disorders follow a similar pattern, as does PTSD: while the narrative in clinical trials often centres on veterans, women experience PTSD at twice the rate of men, often due to past sexual abuse or childhood trauma.
When it comes to addiction, women with substance use disorders develop addiction more rapidly after first use, experience higher rates of trauma and gender-based violence, and face greater stigma and structural barriers seeking treatment. There are also conditions that are exclusive or predominant to the female sex: premenstrual dysphoric disorder (PMDD), perinatal depression, and the mental health burden associated with endometrioses, for which psychedelic treatments are only now beginning to be explored, often by organisations operating at the field’s margins precisely because mainstream research has not prioritised them.
The evidence gap
Psychedelic research, despite its progressive reputation, has largely inherited the same structural blind spots as the rest of biomedical science. Current data presented during Blest-Hopley’s keynote highlighted that women make up only 18-36% of participants in psychedelic clinical trials – a figure that is particularly shocking given that women bear a disproportionately high burden of the mental health conditions psychedelic treatments are designed to address.
As Blest-Hopley put in her keynote, women are also statistically more likely to experience adverse reactions during psychedelic trials that current protocols have not been designed to account for, and 50-75% of those adverse reactions go unaccounted for in the existing data.
But just including women won’t solve the issue. Blest-Hopley emphasised a critical distinction during her speech: the issue is not simply that women have been excluded, but that even when they were present in studies, the field failed to look closely at their data. “Many of [the studies] included women, but they did not look into the data that was recorded,” said Blest-Hopely. So even though women are technically present, they remain scientifically invisible as their experiences are overlooked or simply absorbed into a dataset that was not designed with them in mind.
Then there are the questions that few researchers have even thought to ask. For example, psychedelics interact with hormonal systems in ways that current trials have barely begun to investigate. The phase of a woman’s menstrual cycle can affect how a psychedelic is metabolised and experienced, drug sensitivity is generally higher in women, and there is emerging evidence that hormonal contraception can blunt or alter the psychedelic experience altogether. The implications of these gaps for the safety of women using psychedelics, their dosage, and therapeutic outcomes remain largely unknown.
A scoping review published in the International Journal of Drug Policy captured the scale of this omission. After analysing 75 studies on the use of psychedelics for substance use disorders spanning more than 60 years, the authors found that only 18 studies had samples that were close to being sex-balanced, nine included no women at all, and not a single study analysed sex or gender differences in its discussion section.
We already knew that there is a grave issue of systemic bias in medical research and funding (for example, erectile dysfunction currently receives five times more funding than researching endometriosis, a condition affecting one in ten women globally). Psychedelic science has arrived into this system, and, so far, it has not found a way out of it.
Minorities and gender diverse people
The representation crisis in psychedelic research does not begin and end with women. A final panel session at the ICPR 2026, “Psychedelics in Context: Gender and sexual diversity, precarity, and power”, made it increasingly clear that these omissions are intersecting and compounding. The further a person is from the white, male default of the clinical trial participant, the less the evidence speaks to their experience.
Researcher Sabrina Cluesman presented work on ketamine-assisted group therapy designed specifically to address identity-related trauma in transgender and gender-expansive adults, a population that experiences PTSD at significantly higher rates than the general population, alongside disproportionately high rates of depression, anxiety, and suicidal thoughts – driven largely by discrimination, minority stress, and gender-based violence. They are among those with the highest need for effective mental health intervention, and among those least represented in the research that is supposed to generate it.
For this population, the clinical infrastructure of psychedelic treatment is almost entirely unadapted. As Cluesman pointed out, clinical frameworks typically can’t properly gender these patients, and often lack tools to meaningfully account for abuse history in informed consent processes. And because the psychedelic experience does not happen in a social vacuum, for gender diverse people navigating a world that frequently denies their identity, encountering another system that cannot acknowledge who they are impacts their therapeutic experience.
The statistics are just as grim when it comes to the exclusion of racial and ethnic minorities and immigrant populations. Research from the US found that between 1993 and 2017, 82.3% of psychedelic research participants were non-Latino white. Immigrant and displaced populations are almost entirely absent from the data.
Ronica Mukerjee, an abolitionist, harm reductionist, and one of the most compelling voices at ICPR 2026, noted that only 4.8% of psychedelic studies track immigrant status. This is not incidental. It reflects a research design created for and by a very specific type of person, and one that has struggled to extend beyond it. This systematic exclusion in participants is a reflection of the research centres themselves: 88% of psychedelic research centres are white-led, and 92% of them have white men in charge.
“Our job is not to get people to fit in”, Mukerjee said during the conference’s final panel on gender, precarity, and power.
