Psychedelic research is evolving, and so does the discussion around its biases. The young field is host to some of the more interesting and stubborn methodological issues. The experiential side of psychedelics poses new challenges to clinical studies, such as the blinding problem and dealing with the dominance of set and setting.
In the realm of theory, psychedelic research brings together diverse fields, from medicine and psychology to anthropology and philosophy. With this interdisciplinarity come different concepts, research methods, and protocols. This state of affairs enriches and complexifies the field, but also makes it difficult to create joint standards.
This article dives into the sea of biases in psychedelic research and offers some solutions. Philosophy of science shows us that our image of science as objective and bias-free can be quite misleading. So, before going into the specificity of psychedelic research, it is useful to get familiarized with some of the well-known biases that are common in other fields of study.
The Researcher is the Norm
One of the most famous biases in psychology is the focus on samples from WEIRD populations. WEIRD stands for Western, educated, industrialized, rich, and democratic societies, and research shows that the vast majority of individuals recruited for studies and trials in Western countries share this background. The assumption is that the data is generally applicable, but we know that members of WEIRD societies “are among the least representative populations one could find for generalizing about humans”.
In the immediate term, the lack of diversity is problematic because other groups and societies are underserved. We may discover in hindsight that members of those groups respond differently to a treatment or have different needs altogether. Thus, a treatment might be less beneficial for them and may even cause harm.
The WEIRD bias carries long-term consequences as well. Based on results from experiments with a narrow and specific dataset, researchers build generalized theories about the human psyche and behaviour. The theories become the basis for our understanding of humans and our definitions of what is considered normal, healthy, and accepted. In other words, we attach objectivity and generalizability to our data and theories, while the data reflects our subjective positioning. Further down the line, theories can become powerful normative standards, supposedly based on proven scientific facts.
Let’s Talk About Sex
In the same way we neglect to consider relevant cultural factors, we can be blind to biological ones. The opening lecture of the 2026 Interdisciplinary Conference on Psychedelic Research (ICPR) was titled “The 51% blind spot: Psychedelics, women's health and the opportunity we must not miss”. Neuroscientist Grace Blest-Hopley explained that while females are recruited to psychedelic studies, their distinct biology is mostly not taken into account.
For example, hormonal fluctuations during the menstrual cycle can influence neurochemistry, including 5-HT2A receptor expression, cognition, mindset, experiential intensity, and psychological responses. Females undergoing perimenopause and menopause are often excluded from trials, which means that the data on those populations is thin. Data on the menstrual cycle and on hormonal states are usually not collected, so even if there is valuable information to be found, we are not looking. Here again, generalized conclusions and theories are drawn based on a mixed dataset of males and females, without accounting for their (potential) differences.
Money Makes the World Go Around
Another type of bias is related to financial conflicts of interest. The classic example here would be a study about the efficacy of a psychedelic compound sponsored by a pharmaceutical company pursuing a patent. This type of bias is relevant to any scientific field, yet the historical and often contemporary lack of federal funding for psychedelic research makes it more vulnerable, as it often relies on financing from interested pharmaceutical companies, industry, and philanthropic funders. Such conflicts of interest pose a potential threat to the independence, autonomy, and integrity of the research and have been shown to have an effect on results and on the reporting of adverse events.
The lack of financial resources is responsible for more biases. Supplying medical supervision and psychotherapy throughout the psychedelic experience makes psychedelic trials expensive. To stay within budget, many researchers need to draw their conclusions based on a small sample. This brings us back to the generalizability issue. Research over a long period of time calls for even more resources, and its interests sometimes exceed those of the funders. Yet without long-term findings, we are seeing a very partial picture.
When research is looked upon primarily through a financial lens, that is, in terms of efficiency and profitability, attempts to reduce costs include waiving integration or the psychotherapy part altogether. We then draw conclusions on the efficacy of a certain molecule, without considering the effect of the lack of support in itself on participants’ safety and on the results of the experiment.
The Rabbit Hole of Psychedelic Biases
Unequal representation, generalizability, and financial conflicts of interest are biases found in various scientific fields, but psychedelic research faces some specific challenges. Perhaps the most discussed one relates to controlling the placebo effect. The placebo effect concerns a genuine improvement in symptoms of patients who didn’t receive the pharmacological agent.
Placebos were effectively used in medical practice long before the placebo effect received its name and became established in an article from 1955. It is conceptualized as resulting from cues captured from the context: the medical environment, clinicians’ body language, facial expressions, the language used to discuss expected drug effects, the size, price, and colour of pills, and so on. In other words, a placebo is the set and setting of the medical world.
Contextual factors seem to play a major role in determining results, similarly to how set and setting influence the psychedelic trip. The ‘set’ component of a placebo includes expectations, feelings, and beliefs people have in relation to the treatment. Together, they work as what we colloquially call a self-fulfilling prophecy. For example, in the psychedelic context, the media hype around psychedelics as powerful remedies creates strong beliefs and high expectations, which in turn affect trial results.
In response to the placebo theory, Randomized Controlled Trials (RCTs) were established as an accepted method for getting medicines approved. RCTs have structures and protocols in place to make sure that placebo-related biases are controlled for. In order to get a new pill approved, it would usually be tested on two groups, one receiving the new drug and another receiving an identical-looking pill without the pharmacological benefits. None of the participants, and often none of the researchers, know who was assigned to which group – this is called blinding. The new drug would have to significantly outperform the placebo pill in order to be approved.
In psychedelic trials, successful blinding is very difficult to achieve. When geometric forms begin to fractalize into colourful dinosaurs, most people guess correctly that they were not in the placebo group. If people know they got “the real thing”, it becomes difficult to judge if their symptoms improved due to the drug or to the placebo effect. This was one of the reasons the FDA supplied for rejecting Lykos Therapeutics’ application for MDMA-assisted psychotherapy for PTSD.
Like set and setting, the placebo effect can work both ways. It can generate real improvement for participants who believe they got a cure, but it also has a darker, less familiar twin: the nocebo effect. Nocebo is the placebo’s flipside: participants who know (or discover later) that they were part of the placebo group experience a worsening of their symptoms. These patients come out of the trial worse off than when they arrived, so the nocebo effect raises ethical issues as well.
The experiential aspect of psychedelics made blinding one of the most well-known and difficult issues to tackle in psychedelic science. In order to solve it, researchers are coming up with creative ideas, like using small active doses as the placebo, giving the treatment while patients are asleep, and even developing non-hallucinogenic psychedelics.
The WEIRDos of Psychedelic Science
The psychedelic field has its own WEIRD problem. If we think of the WEIRD bias as recruiting people from your in-group, the in-group of psychedelic research is participants with previous psychedelic experience. When researchers turn to their network for recruiting, experienced people are over-represented. When they recruit online, the volunteer bias shows that people with previous experience volunteer more often to participate in surveys related to psychedelics.
The problems associated with experienced people are that they usually have strong positive feelings about psychedelics, which can influence trial results through their set and the placebo effect. Their familiarity with the psychedelic altered state also means that they break blinding attempts more easily. Like in the WEIRD case, results based on participants with experience cannot be generalized.
Experience features as a bias on the researcher’s side as well. Researchers with previous psychedelic experience have been accused of letting their “excessive enthusiasm” influence results and reporting. At the other end, inexperienced researchers are blamed for their scepticism and opposition, resulting from the negative stigma and wild history of psychedelics. Here too, trial results can get affected, and collaboration between researchers can become difficult. It seems like previous experience matters whether you have it or you don’t. This poses a real credibility issue for psychedelic research.
A Lab is Just Another Setting
The theories of placebo and of set and setting are in agreement that context always has an effect. In this sense, the lab and the hospital are far from neutral – they are the setting of clinical research. A hospital comes with white cloaks, a certain design, and distinct smells, which are all culturally associated in our minds. For locals, the hospital may also carry a variety of memories, from losing someone close to giving birth to a child. For local patients, it may be associated with all the failed treatments they have tried in the past.
Then there is the specific setting where the trip takes place, which varies across experiments. Some researchers try to make the room cozy, with a sofa and some plants, for example. In other studies, participants’ setting is the inside of an MRI machine. This is a very different experience from eating some mushrooms in nature. So, how much of the results relate to the substance and how much to the setting in which it was taken, and can those two even be separated?
A clinical setting is supposed to supply us with a neutral environment, a place where “all other things being equal”, so that we can make a valid conclusion. With psychedelics, nothing in the setting is ‘neutral’ in that sense. Like with the WEIRD bias, the results we see are a reflection of ourselves, this time of how we do science.
The more seriously we take the theories of placebo and set and setting, the more we realize how biased we actually are. It is not that researchers are sloppy (well, some of them are), but if the context plays such an important role, there is hardly a way out. Everything matters, from the people present to the furniture, the size of the room, and the color of the walls. There’s only so much a researcher can do about the hospital’s design.
In order to overcome some of these difficulties, we need to know more about the settings of trials. In 2025, a group of researchers created the ReSPECT guidelines: Reporting Setting in Psychedelic Clinical Trials, to raise awareness and help researchers by supplying a standardized framework for reporting contextual elements. If this becomes widely applied, contextual data can become clearer, hopefully contributing to a more exact science.
From One to Ten, Rate Becoming One with the Universe
Consciousness studies is a whole research field occupied with the question of what consciousness is and how it works. While we are very far from cracking this one out, we use the term ‘consciousness’ abundantly in psychedelic research, supposedly all referring to the same thing. Yet the concept carries different histories and meanings to researchers from psychology, neurocognitive science, or religious studies.
This problem is not unique to the concept of consciousness. The term entropy, for example, is frequently used in psychedelic literature, while it actually carries two different meanings. The first reference is drawn from information theory, where it stands for uncertainty, and the second from thermodynamics, where it means disorder. Thus, using this ambiguous term creates misunderstandings about the mechanisms and processes taking place during a trip.
In addition to this known issue of interdisciplinarity, psychedelic research faces problems of transdisciplinarity. While interdisciplinarity is a relation between different academic fields, transdisciplinarity refers to relations between the academy and other forms of doing and knowing, such as spirituality, art, and indigenous knowledge.
One example is applying scientific tools and methods to measure ineffable, spiritual, and mystical experiences. In order to understand if there is a link between mystical experiences, transformation, and therapeutic results, we need to have an idea of what a mystical experience is. From here, it is easy to see how things can get entangled. Of course, we can create a scale and measure the level or frequency of ‘the mystical’, but we are still relating to a phenomenon which lies outside the realm of science.
It’s All in Your Mind
Psychedelically enough, the deeper you go down the rabbit hole of biases, the more it reflects yourself. It is not only the mindset of participants that influences results, but it is also the mindset of the researcher, including their history, upbringing, beliefs, and perceptions. Together, these factors have a role in shaping the design of studies, research questions, methodologies, analysis, results, and conclusions.
In the Global North, research is mostly based on the assumption that psychedelics are (or can become) remedies for mental health problems. This is not a scientific fact, but an underlying belief propelling research. Beginning from other assumptions, for example, that psychedelics are political tools, spiritual guides, or plant entities, would make for a different kind of research, bringing different results.
Our perception of psychedelics is in itself based upon a plethora of metaphysical beliefs and scientific assumptions. It begins with our ideas about concepts like health and well-being, and goes to fundamentals like the nature of consciousness and the universe. What does this say about science’s claim for objectivity?
Considering that we cannot separate who we are from how we think, this bias is not one to battle, but one to learn to work with. A plurality of backgrounds and worldviews also has its advantages. It produces a richer variety of scientific investigations and opens a path for new ways of thinking and doing. Variety doesn’t eliminate our cultural biases, but it highlights and mitigates them.
If we accept that absolute objectivity does not exist, self-awareness and integrity become important tools to help us better understand and report influential factors like setting and positioning. The good news is that researchers keep discussing biases and suggesting possible solutions. All these pitfalls are also opportunities to make our research methods and trial designs better. It’s almost like science itself has taken a psychedelic, inspiring insight, self-reflection, and creativity.