Examining Attitudes to Psilocybin: Should Candidates for Medical Psilocybin be Required to Pass a Contextual Suitability Test?

Abstract

Due to increasing evidence of efficacy in treating mental health disorders, psilocybin may become a legal medicinal drug. This study tested the validity of Carhart-Harris and Nutt’s (2017) model of extra-pharmacological (EP) factors. It examined whether such factors should be considered in any psychological suitability test for medicinally prescribed psilocybin. Two hundred nineteen participants (101 self-identified females, 109 males, seven nonbinary people, and two who preferred not to say), in an age range of 18 to 68 years, completed three online measures of personality—Set, Setting, and Intention—and the Attitudes Toward Psilocybin (ATP) scale. The sample was equally divided between those who had used psychedelics (52.1%) and those who had no previous psychedelic use (47.5%). A series of stepwise linear regressions were run to examine whether EP factors predicted ATP scores. The ATP scale was tested for reliability, construct validity, and determinant validity and was deemed an appropriate measure. A model consisting of a positive Set, Openness to Experience, and lower Extraversion significantly predicted ATP scores. These findings supported the EP model and suggested that a suitability test may be a useful tool when determining whether a prescription of psilocybin is an appropriate course of treatment.

Keywords

psilocybin mental health disorders psychopharmacology personality

Introduction

Psychedelic substances are steadily making the transition from being viewed negatively as illegal drugs to being viewed as potential medicines. Several trials support their therapeutic potential (e.g., Griffiths et al., 2016; Johnson & Griffiths, 2017; Stroud et al., 2018). The U.S. Food and Drug Administration has designated psilocybin-assisted psychotherapy as a “breakthrough therapy” for treatment-resistant major depression (Aday et al., 2019). A randomized, double-blind trial has been launched across Europe and North America to investigate the efficacy of psilocybin in treatment-resistant depression (Kelly et al., 2019).

Set, Setting, and the Effectiveness of Psilocybin

Unlike “conventional” medical treatment, the effectiveness of psilocybin is not just dependent on dose and type. It is dependent on a range of extra-pharmacological (EP) factors, which are also important in predicting treatment outcomes. EP factors include the person’s state of mind immediately prior to taking a psychedelic (“Set”), the environment in which the person takes the substance (“Setting”), and their “Intention” for the experience (Carhart-Harris et al., 2018; Fadiman, 2011; Haijen et al., 2018; Studerus et al., 2012). The importance of Set and Setting is commonly credited to Timothy Leary (Leary, 1963). Leary et al. (1965) suggested that with a favorable Set and Setting, psychedelics could produce a shift in everyday consciousness, which could, in turn, provide insight concerning repetitive thought patterns or behaviors, opening the mind to alternative perspectives.

When discussing the ideal Set and Setting, Gerald Heard (1960, as cited in Leary et al., 1965, p.65) suggested that the individual should be

. . . concerned but not anxious, interested but not engrossed, diagnostic but not critical, aware of the seriousness and confidential value of what is being conveyed and all the more incapable of coldness or shock, aloofness or dismay [. . .] Any sense of fear or alien-ness means that the root danger and origin of all breakdown, i.e., separation is present.

More recently, Hartogsohn (2017) discussed the importance of Set and Setting, in that “the effects of psychedelic drugs are dependent first and foremost upon Set (personality, preparation, expectation, and intention of the person having the experience) and Setting (the physical, social, and cultural environment in which the experience takes place)” (p. 1).

The EP Model

To incorporate the Set and Setting hypothesis, Carhart-Harris and Nutt (2017) put forward a model of the impact of EP factors (EP model) on the outcome of psychedelic use. It considers how individuals’ personality traits, pre-state mindset (e.g., the Set and the Setting in which the drug is taken), Intention, and the dosage combine to affect the medicated state and long-term outcomes (see Figure 1). The study of the EP model of psychedelics exists within the context of an overall Humanistic approach to experience and medical intervention. In fact, the Journal of Humanistic Psychology did a special issue on the topic in 2017 (Grob & Bossis, 2017). Empirical research has supported the EP perspective. For instance, a qualitative analysis of participant experiences in psilocybin-assisted psychotherapy indicated core themes of relational embeddedness, emotional range, the role of music as a conveyor of experience, meaningful visual phenomena, wisdom lessons, and revised life priorities (Belser et al., 2017), all familiar concepts within Humanistic Psychology.

Figure 1.

The Extra-Pharmacological Model of Drug Action.

Within the framework of the EP model, if an individual has a more positive attitude, in general, toward psilocybin (ATP), then that positive attitude will positively influence an individual’s Set immediately prior to taking psilocybin (Carhart-Harris & Nutt, 2017). A positive Set, in turn, increases the likelihood of more positive long-term outcomes of the treatment. Conversely, a less positive or negative attitude will negatively influence an individual’s Set, which increases the likelihood of a challenging or aversive experience.

Psilocybin as a Legalized Medical Treatment

In the context of psilocybin becoming a legal treatment for certain mental disorders, a general practitioner (GP) or psychiatrist may first be required to assess the psychological suitability of a candidate for such a course of treatment. If psilocybin is proved to be a viable and legal treatment for psychiatric disorders, an individual with certain personality traits and ATP may not be a suitable candidate for a prescription (Erritzoe et al., 2018; Sutin et al., 2013; Terracciano et al., 2008; Turiano et al., 2012). Therefore, data surrounding the suitability of specific candidates for a course of treatment that involves a prescription of psilocybin medication may be important to help minimize harm and maximize the potential of benefit.

The Present Study

The aim of this study was to explore the potential suitability for a prescription of psilocybin medicine among a sample of participants taken from the general population. The basis of this research is that individuals with a negative ATP, and those who have a poor understanding of the EP factors, are less likely to be suitable candidates for a prescription of psilocybin (Carhart-Harris et al., 2018).

In line with the EP model, this study examined participants’ ATP, their personality, their Set if they were to hypothetically take psilocybin, and their understanding of the effects of the Setting in which they would hypothetically take psilocybin.

Hypothesis 1 (H1): ATP scores would positively correlate with Set, Setting, and Intention scores.

Hypothesis 2 (H2): Higher levels of personality traits, Extraversion, Agreeableness, and Openness to Experience would predict higher ATP scores.

Hypothesis 3 (H3): Higher levels of personality traits Conscientiousness and Emotional Stability would predict lower ATP scores.

Hypothesis 4 (H4): A model of personality traits, namely, Extraversion, Agreeableness, Openness to Experience, higher Set, Setting, and Intention scores, would predict higher ATP scores.

Method

Research Design

This was a quantitative study using a correlational design with additional predictive models. Participants were recruited using convenience sampling and web-based data collection. The data were collected from participants through an anonymous online survey. The independent variable was ATP scores, and the dependent variables were Personality, Set, Setting, and Intention.

Participants

Power analysis indicated that a sample of 170 participants would be required to detect a moderate effect size with a power of .8 and six predictor variables. Participants for the study were recruited using opportunity sampling. A total of 262 responses to the online survey were recorded, with the age range being 18 to 68 years. One participant withdrew consent, and 42 participants did not complete the survey, so these participants were removed from the data set. Two hundred nineteen participants remained, with an age range of 18 to 68 years (M = 32.31, SD = 11.99). Of the 219 remaining participants, 109 were male (49.7%), 101 were female (46.2%), seven identified as nonbinary (3.2%), and two preferred not to say (0.9%). The mean age of the participants was 32 years (M = 32.31, SD = 11.99). As outlined in Table 1, the sample was close to equally divided between those who had used psychedelics (52.1%) and those who had no previous psychedelic use (47.5%). Of those who had tried psychedelics, less than half had experience with psilocybin (39.8%), facilitating the exploration of how previous experience influenced attitudes. These data described a young sample, evenly divided between males and female genders, primarily based in the Republic of Ireland. The majority were college-educated and fully employed and did not report a history of psychiatric diagnoses.

Table 1.

Demographic Details.

Variable	Group	n (%)	Variable	Group	n (%)
Employment status	Full-time	118 (53.9)	Any psychiatric history	Yes	75 (34.2)
	Part-time	63 (28.7)		No	139 (63.5)
	Unemployed	38 (17.4)		Prefer not to say	5 (2.3)
Previous psychedelic experience	Yes	114 (52.1)	Previous psilocybin experience	Yes	87 (39.8)
	No	104 (47.5)		No	131 (59.8)
	Prefer not to say	1 (0.4)		Prefer not to say	1 (0.4)
Gender	Male	109 (49.7)	Nationality	Republic of Ireland	137 (62.6)
	Female	101 (46.2)		Europe	32 (14.6)
	Nonbinary	7 (3.2)		Outside EU	49 (22.4)
	Prefer not to say	2 (0.9)		Prefer not to say	1 (0.4)
Residing in	Republic of Ireland	137 (62.6)	Education level	No schooling	1 (0.5)
	Europe	32 (14.6)		Some schooling	53 (24.2)
	Outside EU	49 (22.4)		Undergrad degree	107 (48.9)
	Prefer not to say	1 (0.4)		Postgrad degree	52 (23.6)
				Doctorate or PhD	6 (2.8)
Currently a university student	Yes	68 (31.1)
Currently a university student	No	151 (68.9)

Note. EU = European Union.

Materials

Data from three measures were collected using Qualtrics online survey software (Qualtrics, 2021).

Ten-Item Personality Inventory (TIPI)

This was designed by Gosling et al. (2003) as a measure of the Five-Factor Model (FFM) of personality. This scale comprises 10 items, measuring five different personality constructs (Openness to Experience, Conscientiousness, Extroversion, Agreeableness, and Emotional Stability).

Set, Setting, and Intention Scale

This scale was designed by Haijen et al. (2018), who based the scale on the work of Russ and Elliott (2017). This scale comprises 12 items, which were split into three sections: seven Set questions, three Setting questions, and two Intention questions (see Supplemental Table 5 for the scale items for the Set, Setting, and Intention Scale and the ATP Scale). Haijen et al. (2018) conducted a principal component analysis of the 12-item scale, indicating a three-factor structure in line with the above subscales. The Kaiser–Meyer–Olkin measure of sampling adequacy was 0.800, and Bartlett’s test of sphericity was highly significant, χ²(66) = 941.23, p < .001, indicating that the data were suitable for a principal component analysis (Budaev, 2010). The three-factor structure explained 54.33% variance cumulatively. The variance explained by each (a) “Set,” (b) “Setting,” and (c) “Clear Intentions” was respectively, 31.12%, 12.49%, and 10.72%. The external validity of the measure was supported in the same study as indicated by its significant prediction of a positive outcome from psychedelic use in line with hypotheses.

The Set, Setting, and Intention Scale items were modified for this study because, unlike Haijen et al. (2018), the participants in this study were not going to ingest any substance. Instead, they hypothesized how they would approach Set, Setting, and Intention if they were about to take psilocybin. Participants rated how much they believed each statement applied to them on a scale of 1 (strongly disagree) to 7 (strongly agree). Internal reliability for the scale is described in Table 2. Each of the subscales meets the criteria for appropriate internal reliability.

Table 2.

Descriptive Statistics for Scales.

Measure	M	SD	Skewness	Kurtosis	Range	Cronbach’s α
ATP	53.078	16.950	−0.260	−1.057	66.00	.938
Set	28.813	12.144	−0.198	−1.217	42.00	.920
Setting	19.365	2.940	−3.199	12.527	18.00	.865
Intention	8.932	2.913	−0.595	0.013	12.00	.590
Extraversion	8.356	3.278	−0.011	−0.916	12.00	.761
Agreeableness	10.228	2.241	−0.111	−0.640	10.00	.230
Openness to experience	10.910	2.136	−0.390	−0.847	8.00	.305
Conscientiousness	10.539	2.574	−0.683	0.005	11.00	.532
Emotional stability	8.726	2.931	−0.081	−0.692	12.00	.632

Note. ATP = attitudes toward psilocybin.

ATP

As no previous scale measured “Attitudes Toward Psilocybin,” a specific scale was developed for this research. It was based on scales measuring similar constructs with alternative substances (Campbell & Chang, 2006; Forstmann & Sagioglou, 2017). Specifically, it drew on the four “Positive Bias Toward Psychedelic Use” items used in Haijen et al. (2018). Internal reliability for Positive Bias Toward Psychedelic Use items has been reported as α = .78 (bootstrap 95% confidence interval [CI] = [0.75, 0.81] for 1,000 samples; Hübner et al., 2021). External validity for the Positive Bias Toward Psychedelics Use items can be seen in its prediction of well-being scores following acute psychedelic experiences, in line with the hypotheses (Haijen et al., 2018). However, a lower Positive Bias Toward Psychedelics did not predict attrition from the study (Hübner et al., 2021). The “Attitude Toward Psilocybin” scale used in this study is an 11-item scale focused on individuals’ overarching attitudes (knowledge, thoughts, feelings, and opinions) toward psilocybin. Reliability and validity are reported in the “Results” section (see Supplemental Table 5 for the ATP items). Higher ATP scores indicate more positive ATP.

Ethics

Ethical approval was obtained from the University College Dublin’s Research Ethics Committee.

Results

Preliminary Analysis

Exploratory psychometrics were conducted on the novel ATP scale to test for scale validity. A Pearson correlation was used to test for convergent validity by examining whether the four items drawn from Haijen et al. (2018) were related to the ATP. A strong significant relationship was observed (r = .925, p = .000). Users were categorized according to their previous psychedelic experience to test for discriminant validity. The expectation was that those with no psychedelic experience would have the least positive attitude scores toward psilocybin, that those with experience with psychedelics would have more positive attitudes, and that those with experience with psilocybin would have the most positive attitudes of the three groups. A significant difference was observed between the groups (F = 100.703. p = .000). Scheffé post hoc testing indicated a significant difference in the predicted direction between all groups. The results of these psychometrics supported the discriminant validity of the scale, as the groups differ in the expected direction. The decision was made to use the self-created ATP scale in this study.

Most measures had acceptable Cronbach’s alpha, except for Agreeableness and Openness to Experience. As these subscales comprised only two items, it was inappropriate to delete one of them. Therefore, the results of these subscales should be interpreted with caution due to their low reliability. Skewness, kurtosis, and an investigation of histograms indicated the normal distribution of the data (see Table 2 for Descriptive Statistics).

Primary Analyses

Hypothesis 1 predicted that ATP scores would positively correlate with Set, Setting, and Intention scores. There was a strong positive relationship between Set and ATP scores, with 69.89% amount of the variance being accounted for by Set. There was a weak positive relationship between Setting and ATP scores. There was a moderate positive relationship between Intention and ATP (see Table 3).

Table 3.

Correlational Matrix of Variables.

Variables	1	2	3	4	5	6	7	8
1. ATP
2. Set	.836**
3. Setting	.155*	.085
4. Intention	.552**	.502**	.208**
5. Extraversion	−.187**	−.145*	.022	.041
6. Agreeableness	−.057	.271	.100	−.012	0.37
7. Openness	.420**	.363**	.166*	.211**	.127	.156*
8. Conscientiousness	−.211**	−.205**	.005	−.117	.253**	.223**	.073
9. Emotional stability	−.109	−.014	−.144*	−.071	.300**	.184**	.087	.268

Note. ATP = attitudes toward psilocybin.

p < .05. **p < .001.

A multiple stepwise linear regression was calculated to predict ATP scores based on Set, Setting, and Intention scores. Two models were produced. The first model consisted of Set on its own. A significant regression equation was found, F(1, 217) = 503.982, p = .000, with an R² of .699. The second model consisted of Set and Intention. Setting was not included, likely due to the weak correlation with ATP. A significant regression equation was found, F(2, 216) = 281.157, p = .000, with an R² of .722. Model 2 was rejected because it is likely that Intention had collinearity with Set scores due to the correlation between them (r = .502, p = .000). Model 1 was accepted. Analyses suggest that Set was the stronger predictor of ATP.

Hypothesis 2 stated that the traits of Extraversion, Agreeableness, and Openness to Experience would predict positive ATP scores. Contrary to the hypothesis, there was a weak negative relationship between Extraversion and ATP. There was a moderate positive relationship between Openness to Experience and ATP (see Table 3). A multiple stepwise linear regression was calculated to predict ATP scores based on Openness to Experience and Extraversion scores. A significant regression equation was found, F(2, 216) = 33.196, p = .000, with an R² of .235, indicating that lower levels of Extraversion and higher levels of Openness to Experience predicted ATP scores.

Hypothesis 3 stated that trait Conscientiousness and trait Emotional Stability would predict negative ATP scores. There was a weak negative correlation between ATP and Conscientiousness and no significant correlation between trait Emotional Stability and ATP scores (see Table 3). Linear regression was calculated to predict ATP scores based on Conscientiousness. A significant regression equation was found, F(1, 217) = 10.103, p = .002, with an R² of .044, indicating that lower Conscientiousness predicted ATP scores, although this is unlikely to be clinically meaningful.

Hypothesis 4 stated that traits Extraversion, Agreeableness, Openness to Experience, higher Set, Setting, and Intention would predict higher ATP scores. However, only Openness to Experience, Extraversion, and Set were significant predictors of ATP scores, as evidenced by previous hypothesis testing. Therefore, they were the only three variables included in the regression analysis. A linear regression consisting of Set, Openness to Experience, and Extraversion significantly predicted ATP, F(3, 215) = 187.441, p = .000, with an R² of .723, indicating that a model made of a more positive Set, a greater Openness to Experience, and lower Extraversion scores significantly predicted ATP (see Table 4).

Table 4.

Set, Setting, Intention, and Personality as Predictors of Attitude to Psilocybin.

Parameter	B	SE	t-value	p value
Set	.836	.052	22.45	.000
Openness to experience	.451	.476	7.515	.000
Extraversion	−.244	.310	−4.074	.000
Conscientiousness	−.211	.437	−3.179	.002

Discussion

This study used an approach based predominantly on the studies of Carhart-Harris et al. (2018), Haijen et al. (2018), and Carhart-Harris and Nutt (2017) to explore the suitability of a potential candidate for a prescription of the psychedelic compound psilocybin. Its primary aim was to test the relationship between personality type and the salient contextual factors that affect long-term outcomes of the treatment (Set, Setting, and Intention) while paying particular attention to the effect on ATP. The results of this study partially supported the hypotheses. While correlations were found between ATP scores and Set, Setting, and Intention scores, only Set was a valid predictor. In relation to personality variables, ATP scores were significantly related to traits of Openness to Experience and lower levels of Extraversion but only weakly related to Conscientiousness and were not related to Agreeableness or Emotional Stability. A model of Set, Openness to Experience, and Extraversion predicted a large proportion of the variance in ATP scores.

Implications

In terms of practical application, if clinicians were considering a candidate for a prescription of psilocybin, these data suggest that initially requiring the candidate to perform a psychological suitability test—exploring personality traits and the patient’s understanding of the EP factors—might offer valuable information that could help the clinician discern whether that course of treatment is appropriate.

This study suggests that, alongside control studies of psilocybin to assess its effectiveness for mental health difficulties, studies should also examine the impact of EP factors as key mediators of treatment outcomes. However, it should be noted that this study utilized a research design based on hypothetical psilocybin use, and the findings can only be tested adequately through control studies of psilocybin.

Strengths, Limitations, and Future Research

This study had several limitations. The hypothetical nature of the study design, due to the current legal status of psilocybin, meant that no data could be collected, which would have indicated how a person’s attitude influenced a real psilocybin experience. If such data could be collected, the research could further explore how a person’s attitude may affect their suitability for a prescription of psilocybin.

Several exploratory psychometrics were conducted on the novel ATP scale. These tests explored the scale’s reliability, the discriminant validity, and the exploratory convergent validity. Based on the results, the decision was made to proceed with the scale in the format in which it was developed. However, the results of these analyses are only indicative and exploratory, so if the scale is to be used in future studies, an exploratory factor analysis of the scale is recommended as it may highlight further information about the scale’s use and usefulness.

Furthermore, the study relied on opportunity sampling and self-report measures, which may have led to biased results. A significant number of participants in the sample were self-selected through online forums whose users tend to have psychedelic experiences and thus are more likely to hold positive views toward psychedelics and psilocybin. These data described a young, White sample primarily based in the Republic of Ireland. The majority were college-educated and fully employed and did not report a history of psychiatric diagnoses. The sample is not representative of the general population, even within the Republic of Ireland (which has a largely homogeneous White ethnically Irish population). Nor was the sample representative of those who present to GPs seeking support for mental health difficulties. This research needs to be replicated with more racially and ethnically diverse samples to increase its generalizability.

A strength of this study is that half of the sample had never taken psilocybin before, allowing the research to test between-group hypotheses. These results are in line with previous studies that suggest that a positive Set toward psychedelics is an important factor to consider when studying the effects of psilocybin (Carhart-Harris et al., 2018; Haijen et al., 2018; Hartogsohn, 2017).

Conclusion

Although the EP model for predicting acute and long-term drug effects has only recently been formally developed within the academic literature, the importance of a suitable Set and Setting has been well known to psychedelic users since the 1960s (Carhart-Harris et al., 2018; Haijen et al., 2018; Wark & Galliher, 2010). This study offered the first analysis of how an individual’s personality traits and knowledge of the salient contextual factors (Set, Setting, and Intention) surrounding psilocybin usage can affect an individual’s attitude toward the substance. That attitude may influence the quality of the acute “intoxicated” state and subsequent long-term outcomes of treatment (Carhart-Harris & Nutt, 2017; Haijen et al., 2018). The findings in this study suggest that administrating a suitability test that considers attitudes in a more in-depth manner may be an important measure to minimize harm and maximize the potential of a beneficial therapeutic outcome of a course of psilocybin treatment. Future studies need to assess EP factors prior to actual psilocybin treatment and examine the relationship to treatment outcomes.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Keith Gaynor

Roisin McNamara

Supplemental Material

Supplemental material for this article is available online.

Author Biographies

Mark Molumby completed his degree in psychology at University College Dublin in 2020 and is currently studying for a master’s in counseling and psychotherapy at Dublin Business School. He practices an integrative and holistic approach to mental health and is a practicing yoga and meditation instructor working in an acute psychiatric hospital in Dublin. He is particularly interested in researching psilocybin. In particular, he is interested in studying psilocybin’s ability to induce ego dissolution and mystical states, with a view to gaining a better understanding of its use as a treatment for a myriad of mental health disorders such as posttraumatic stress disorder (PTSD), chronic anxiety, depression, and addiction.

Keith Gaynor is an assistant professor in the School of Psychology and is a member of the Clinical Psychology Training Programme. He is also a senior clinical psychologist in Dublin East Treatment and Early Care Team (DETECT), Early Intervention in Psychosis Services. His research interests focus on mental health, in particular, psychosis, suicidality in those aged below 18 years, and well-being in aviation.

Roisin McNamara has a BSc in psychology and MPsychSc in psychological science from the University College Dublin. She has gained experience working as a research assistant on a range of different projects, with key interests in youth mental health and stigma. She is currently working on a Higher Education Authority (HEA)-funded Innovation and Transformation Project, creating and standardizing a national data set for student counseling services in Irish Higher Education Institutes.

Suzanne Guerin is professor of research design and analysis in the School of Psychology at University College Dublin. She completed her PhD in the School and joined the staff team as a lecturer in 2000. Her research interests cluster under the heading of Applied Health Research and Evaluation and she is involved in a number of projects in areas including intellectual disability, palliative care, and health services research.

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