Enthusiastic users report much more benefit from psychedelics than a more general sample.

There is a new scientific article which investigates the extent to which selection bias may influence the reported benefits of psychedelic experiences.

In it, we discuss:

Much research into psychedelics involves participants who already have a keen interest in psychedelics. This can give a distorted picture, as it is precisely this group that is more likely to have positive expectations, favourable conditions of use and motivations for personal growth. The authors therefore wanted to investigate whether people from an enthusiastic user group actually report a greater positive impact on their quality of life than a more general sample.

The main focus of this article is not on clinical treatment, but on research design and interpretation. The researchers compared two groups of people with previous psychedelic experience: a convenience sample of enthusiasts and a more general population sample recruited via Prolific. In total, 1,182 participants completed an online questionnaire on the perceived impact on quality of life, mindset, setting, motivation and personality.

The results show that the group of enthusiasts reported a significantly more positive impact on quality of life. The difference was significant, with an effect size of d = 0.84. In addition, these participants scored higher on openness, extraversion and agreeableness, reported more favourable mindset and setting, and more frequently cited personal growth as a reason for using the programme.

Even after statistical adjustment for these factors, the difference between the two samples persisted. In the ANCOVA analysis, group membership was found to be the strongest predictor of reported impact on quality of life, followed by setting, motivation, openness and mindset. According to the authors, this means that research that relies heavily on enthusiastic users is likely to show systematically more positive outcomes than research with more representative samples.

It is important to note, however, that this is a cross-sectional online survey based on self-reporting. The article therefore does not demonstrate any objective improvement in health, nor does it show any causal effect of psychedelics. Above all, it shows that the way in which participants are recruited can have a significant impact on how positive the results appear.

In a nutshell: this article shows that psychedelics are likely to appear more beneficial in research when mainly enthusiastic users are recruited, and that more representative samples are therefore important for a fairer picture. It is, of course, logical that people who are keen to go on a trip and have positive expectations experience greater benefits (partly thanks to the placebo effect).