Personalised Perception: The Effect of Personality on the Sensory Effects of Psychedelics

ABSTRACT

Introduction

Psychedelics induce a wide range of sensory distortions and hallucinations (henceforth ‘distortions’). Yet, little is known about factors that influence the occurrence of certain distortions. Extra‐pharmacological variables including personality traits have been found to correlate with the occurrence of different subjective features during the acute psychedelic state. The current study aimed to examine the correlations between personality scores and the intensity of different distortions.

Methods

Four hundred and twenty‐six psychedelic users recruited from Aotearoa New Zealand completed an online survey which examined the intensity of 20 different distortions and measured six different personality traits using the five‐factor IPIP‐NEO‐60 and the 34‐item Tellegen Absorption Scale.

Results

Spearman's correlation analysis and linear regression analysis revealed that the intensity of sensory distortions (including visual trails, objects ‘breathing’, field‐of‐vision changes, visual acuity changes, taste hallucinations, out‐of‐body experiences, experiences of other dimensions, and synaesthesia) was significantly correlated (p < 0.05) and associated with personality trait scores, even when setting, dose, and demographic variables were controlled, although the strength of the association was moderate at best.

Discussion and Conclusions

These findings emphasise the role of personality as a key extra‐pharmacological variable associated with the intensity of certain subjective features of the acute psychedelic state. These findings suggest that personality testing may be a valuable tool for the prediction of acute reactions to psychedelics. This information could be useful to clinicians and therapists in determining effective psychedelic‐treatment approaches.

1. Introduction

Psychedelic drugs are defined by their unique ‘mind‐manifesting’ properties which can produce changes in cognition, perception, sensation, mood and emotion [1, 2]. While the specific mechanisms underlying their effects are not clear, it is understood that the ‘classical psychedelics’, including lysergic acid diethylamide (LSD), psilocybin, mescaline, dimethyltryptamine, primarily exert their effects through 5‐HT_2A receptor partial agonism, although other receptor systems are involved [1]. While the subjective effects are highly variable, psychedelics are perhaps best known for their ability to induce profound changes in sensation and perception. These sensory effects (commonly called hallucinations) can range from slight changes in colour intensity, perceptions of morphing shapes, to fully hallucinated dreamscapes or encounters with non‐ordinary psychedelic entities [3].

While psychedelics have likely been used for millennia [4], in the past few decades psychedelics have received increased attention in Western scientific circles [5]. This ‘psychedelic renaissance’ is largely fuelled by evidence pointing to the therapeutic potential of these substances [6]. Research has shown that psychedelics have the potential to induce lasting positive changes, sometimes after just a single session of psychedelic‐assisted therapy [7]. Studies have found promising results using psychedelic‐assisted therapy for the treatment of treatment‐resistant depression [8], major depressive disorder [9], obsessive‐compulsive disorder [10], substance use disorder [11] and end‐of‐life anxiety [12]. Thus, the prospect of psychedelics becoming legal therapeutic tools is becoming increasingly realistic [6, 13] and has become a reality in Australia [14].

One of the largest issues with the prospect of therapeutic psychedelic use is the considerable unpredictability of the psychedelic experience [13]. More so than other psychoactive substances, the experience induced by psychedelics appears especially sensitive to extra‐pharmacological factors. So‐called ‘set and setting’ encapsulates the internal and external factors that may influence the experience [15]: the user's motivations, past experiences, personality and mood, as well as the physical, social and cultural setting in which the experience takes place [16]. People who use psychedelics in clinical and naturalistic settings already consider these factors in attempts to steer the psychedelic experience towards more positive, comfortable, and therapeutic results [17].

Given the pluripotency of the psychedelic experience, there is considerable disagreement in the literature as to the importance of the nature of the acute experience as a determinant of therapeutic outcomes. The broad consensus is that specific sensory effects of psychedelics (e.g., ‘visuals’) are not especially important for determining therapeutic outcomes [18]. However, some researchers suggest the role of these sensory effects is undervalued, and that they play an important part in determining therapeutic outcomes [18, 19]. These differing conclusions indicate that further research on factors related to the intensity and occurrence of specific subjective sensory features during the acute psychedelic state (APS) is needed. This need highlights the broader limits to current understanding about specific factors that predict acute reactions to psychedelics [6].

One notable extra‐pharmacological factor that may influence reactions to psychedelics is personality. Personality and psychedelic research have been intertwined for decades [20], where much research has examined the effect of psychedelics on the user's personality (see [20]). However, what is less understood is the effect of personality on one's psychedelic experiences. Many studies examining personality and psychedelics have utilised ‘Big Five’ models of personality, which describe personality according to five domains: Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness. Studies using five‐factor models of personality, such as the Revised NEO Personality Inventory (NEO‐PI‐R) [21], have found several associations with personality traits and aspects of the psychedelics experience. For example, one study found that trait extraversion was negatively associated with the frequency of mystical experiences (ME) during the APS [22]. Researchers have theorised that this may be due to the setting preferences of extraverted individuals, where extraverts are more likely to engage in psychedelic use in more social settings (e.g., parties and festivals) which are less conducive to MEs [23]. Additionally, trait neuroticism has been positively associated with the strength of challenging psychedelic experiences during the APS and is predictive of using psychedelics due to peer‐pressure and escapist motivations [24].

Trait absorption seems to be especially relevant to the APS. Usually measured through the Tellegen Absorption Scale (TAS), trait absorption measures an individual's' sensitivity to altered states of cognition, hypnosis, aesthetics and vivid mental imagery. Importantly, it appears that trait absorption is predictive of one's sensitivity to MEs—whether pharmacologically induced or not [25, 26]. Moreover, evidence shows that high trait absorption appears to promote the intensity of all aspects of the APS [13]. That is, individuals higher in trait absorption tend to experience the sensory, emotional and cognitive effects of psychedelics more intensely, whether those effects are positive or not [13]. Trait absorption has also been associated with 5HT_2A receptor sensitivity, possibly providing a mechanism for the increased intensity of the subjective experience [27].

The present study sought to explore the relationship between personality and the subjective psychedelic experience by investigating the relationship between personality traits and the intensity of several subjective features of the APS. Participants from Aotearoa New Zealand completed an online survey regarding demographics, personality variables, drug use, psychedelics drug use patterns and previous sensory experiences with psychedelics.

Correlation and regression analysis were conducted examining the relationship between reported intensity and personality factors. While this study was largely exploratory, it was hypothesised that personality trait variables would exhibit significant associations with the intensity of one or more sensory features, and that these variables would be significantly predictive of this intensity for one or more features.

2. Methods

2.1. Recruitment

Ethical approval for this research was granted by the University of Otago Human Ethics Committee (ET23/032). The data analysed in this article is a subset of data collected and managed using REDCap electronic data capture tools hosted at the University of Otago [28, 29] between 25 April 2023 and 21 September 2023. Participants were recruited through flyers posted around the city of Ōtepoti/Dunedin, and through advertisements posted on online forums such as Facebook, X (formerly Twitter) and Reddit (r/NewZealand).

Participants eligible for participation were required to: be at least 18 years old, speak English fluently, have lived in Aotearoa for at least 1 year, and have taken one of the following psychedelic drugs while in Aotearoa: dimethyltryptamine, LSD, psilocybin, mescaline, salvia divinorum or drugs in the 2C family (e.g., 2C‐B, 2C‐E). Participants who completed the survey were prompted with the opportunity to enter their email address into a prize draw to win 1 of 5 $100NZD e‐vouchers. These email addresses were kept separate from any survey data to maintain anonymity. Winners were randomly selected after data collection was completed.

Seven hundred and seventy participants initially engaged with the survey. Due to an unknown issue with the display logic, data from participants who indicated that they had used psychedelics on more than 100 occasions was lost (n = 49). Data from other participants who initiated the survey was removed due to: (i) insufficient completion of the survey (n = 210); (ii) failed attention checks (n = 37); and (iii) inadequate detail on required questions (n = 48). Data from 426 participants remained and formed the basis of the analyses.

2.2. Design and Variables

After reading an information form and providing consent, eligible participants were presented with the main body of the survey which consisted of five sections: demographic questions, general questions on drug‐use behaviours, the IPIP‐NEO‐60 [30], the 34‐item TAS [24] and questions regarding the subjective features of users' psychedelic experiences.

The order of presentation for the IPIP‐NEO‐60 and TAS was randomised before the survey was published. The IPIP‐NEO‐60 [30] is a 60‐item self‐report questionnaire of the five domains of personality (Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness); 12 items, each with a 5‐point Likert scale, relate to each of the 5 domains. Scores for each of the 12 items are summated (with several items being reverse coded). The final result is a score for each of the 5 domains with a maximum of 60 and a minimum of 12. Higher scores in a given domain correspond to a greater intensity for that domain and its associated characteristics.

The TAS [24] is a 34‐item multidimensional self‐report questionnaire which examines individuals' scores in the personality domain of absorption. The 34 items are all true/false, with ‘true’ responses coded as 1, and ‘false’ responses coded as 0. The final scores range from 0 to 34, with higher scores representing increased absorption.

The final survey section which examined the subjective features explored three categories of features: (i) socio‐cognitive; (ii) emotional; and (iii) sensory. The current article focuses only on analyses of results regarding sensory items which included 20 items: morphing shapes, trails, objects ‘breathing’, colour enhancement, fractals, objects ‘melting’, field of vision (FOV) changes, visual acuity enhancement, out‐of‐body experiences, experiences of other worlds/dimensions, psychoses, synaesthesia, beautiful visuals, disgusting visuals, terrifying visuals, sad visuals, auditory hallucinations, tactile hallucinations, olfactory hallucinations and gustatory hallucinations. The intensity of each of these 20 sensory features was examined in either participants' most intense psychedelics experience to date, or their typical psychedelics experience.

Here, differential display logic was used. Primarily, this was used to differentiate the questions presented to ‘experienced’ participants (those who had used psychedelics on four or more occasions), to those presented to ‘inexperienced’ participants (those who had used psychedelics on fewer than four occasions). Experienced participants were asked to report the typical intensity of a given feature during their typical psychedelic experience—that is, the experience induced by their typical dose of their most used psychedelic within their typical set and setting. Given their low number of total experiences, it was decided that inexperienced psychedelic users would not have a ‘typical experience’ (in the same way as more experienced consumers) on which to base these responses. Therefore, they were presented questions where they were asked to report the intensity of a given sensory feature during their most intense psychedelic experience. The decision to select four psychedelic experiences as the threshold to distinguish between ‘experienced’ and ‘inexperienced’ participants was based on previous discussions and interviews with psychedelic users in New Zealand [17].

All survey items regarding the intensity of subjective features were recorded using either a 5‐ or 6‐point Likert scale. Data from ‘inexperienced’ participants' responses to the question of the intensity of a sensory feature during their most intense psychedelic experience was combined with data from ‘experienced’ participants' responses to the question of the intensity of that sensory feature during their typical psychedelic experience. These combined variables were used in the correlation and regression analyses.

There were two questions which surveyed the dosages of psychedelics that participants used. ‘Typical dosage’ surveyed the dose of a specific psychedelic which participants tended to use most often. ‘Intense dosage’ surveyed the dose administered which resulted in participants' most intense psychedelic experience. Information on how these responses were coded can be found in Table S1.

A text box was presented for both survey items. Most participants gave adequately detailed responses. These were coded on a scale of one to five based on information from the ‘vaults’ of the popular online psychedelic forum Erowid [31]. The codes are as follows: 1 = microdose, 2 = low dose, 3 = standard dose, 4 = high dose, 5 = very high dose. The number of individuals in each category is outlined in Figure S1.

Some participants did not give adequately detailed information to be sorted into these five categories. For example, doses of LSD were often reported in ‘tabs’ (e.g., ‘half a tab’). Out of necessity, the research team made several assumptions in order to code these responses. For example, ‘1 tab’ of LSD was, based on anecdotal report, assumed to be 100ug. Responses pertaining to dosages of psilocybin mushrooms and mescaline cacti were coded on an individual case‐by‐case basis. Those responses that could not be coded despite these assumptions were given a dose code of zero and were removed.

2.3. Statistical Analysis

Survey data was analysed using IBM SPSS 27. Spearman's correlation analyses and stepwise linear regression analyses were also conducted. All 20 sensory variables and all six personality variables met the eligibility criteria for the relevant regression analyses outlined by previous research [32, 33]. For the linear regression analyses, the following variables were included in each model: age, sex, social setting, physical setting, ‘typical dosage’, ‘intense dosage’, trait absorption, trait neuroticism (N), trait extraversion (E), trait openness (O), trait agreeableness (A) and trait conscientiousness (C). For typical physical and social setting, ‘at home’ and ‘alone’ were used as the reference categories respectively. These variables were used to predict the intensity of each of the 20 sensory features.

3. Results

Data from 426 participants was used to conduct the correlation analysis while data from 327 participants was used in the linear regression analyses; participants with inadequate responses to dosage questions were removed from the regression analyses. The sample was a near‐even split of males and females (49.1% and 49.8% respectively). The mean age of the sample was 29.66. Participants overwhelming identified as White/European (85.70%), followed by Māori (11.70%) and other European (11.0%). More details on sample demographics can be found in Table 1.

TABLE 1.

Sample demographics (n = 426).

Demographic	Frequency	Percentage (%)
Sex
Male	209	49.1
Female	212	49.8
Intersex	2	0.5
Prefer not to say	3	0.7
Age, years
18–21	76	17.8
22–25	103	24.1
26–30	96	22.5
31–40	97	22.8
41–50	35	8.1
51–60	15	3.3
60 <	4	0.9
Ethnicity
White/European	365	85.7
Māori	50	11.7
Samoan	8	1.9
Tongan	1	0.2
Cook Island Māori	4	0.9
Niuean	0	0.0
Asian	18	4.5
Other European	47	11.0
Other	4	6.6
Prefer not to say	28	0.9
Religious background
Hindu	4	0.9
Christian	89	20.9
Jewish	4	0.9
Secular/atheist	227	53.3
Muslim	3	0.7
Buddhist	10	2.3
New age/alternative	45	10.6
Other	108	25.4
Region
Auckland—Tāmaki‐Makau‐rau	72	16.9
Wellington—Te Whanganui‐a‐Tara	96	22.5
Canterbury—Waitaha	59	13.8
Otago—Ōtākou	113	26.5
Other	86	20.2
Lifetime mental disorder	189	44.7
Medical condition	110	25.8
Conviction	33	7.7
Drug‐related conviction	11	2.6

Regarding psychedelic use patterns, participants reported that their typical social setting for psychedelics‐use is ‘with a small group of close friends’ (51.4%). The social settings ‘with a single partner’, ‘alone’, ‘at a nightclub/party’, ‘with a group of friends/acquaintances’ were reported as the typical social setting for ~10%–15% of participants. Similarly, participants reported typically using psychedelics at home (theirs or a friend's home; 47.7%), and outdoors/in nature (32.4%). Regarding frequency of psychedelic use, participants reported using psychedelics on 11–20 occasions (20.0%), followed by 21–50 occasions (19.7%), 4–6 occasions (19.2%), and 7–10 occasions (16.9%), 3 or fewer occasions (15.7%), and 51–100 occasions (8.5%).

Table 2 displays the Spearman correlation coefficients between the six personality domains and the intensity of 20 different sensory features of the psychedelic experience. First and foremost, trait absorption exhibited significant correlations with the intensity of all sensory features except psychoses and disgusting visuals. Most of the observed correlation values were relatively low; however, four exhibited correlation coefficients R > 0.3, showing a small but significant correlation [34]. Here, trait absorption was positively correlated with the intensity of FOV changes (r = 0.300), visual acuity enhancement (r = 0.348), visions of other worlds/dimensions (r = 0.315), and synaesthesia (r = 0.332). The correlations observed for the intensity of out‐of‐body experiences (r = 0.288), beautiful visuals (r = 0.263), and olfactory hallucinations (r = 0.266) were also relatively high compared to several of the other associations.

TABLE 2.

Spearman's correlation coefficients between personality trait variables and the intensity of sensory features (n = 426).

Feature	N	E	O	A	C	Absorption
Morphing shapes	−0.021	0.060	−0.005	−0.019	0.072	0.108*
Trails	0.050	0.028	0.068	0.045	−0.017	0.186*
Objects “breathing”	−0.031	0.134**	0.080	−0.045	0.048	0.194**
Colour enhancement	−0.054	0.141**	0.076	−0.034	0.095*	0.159**
Fractals	−0.053	0.111*	0.019	−0.010	0.059	0.128**
Objects “melting”	−0.027	0.085	−0.011	−0.014	0.059	0.162**
FOV changes	−0.039	0.031	0.071	−0.043	0.016	0.300 **
Visual acuity enhancement	−0.075	0.123*	0.109*	0.028	0.053	0.348 **
OBEs	−0.045	0.098*	0.064	−0.017	0.046	0.288**
Other worlds/dimensions	−0.094	0.077	0.058	0.005	0.033	0.315 **
Psychoses	0.090	−0.081	−0.109*	−0.125**	−0.088	0.077
Synaesthesia	−0.064	0.037	0.118*	0.042	0.026	0.332 **
Beautiful visual	−0.033	0.192**	0.175**	0.113*	0.068	0.263**
Disgusting visual	0.109*	−0.056	0.015	−0.100	−0.144**	0.072
Terrifying visual	0.040	−0.031	−0.042	−0.058	−0.079	0.126**
Sad visual	0.042	0.044	0.023	−0.001	0.032	0.170**
Auditory hallucination	−0.029	0.079	0.091	−0.013	0.001	0.155**
Tactile hallucination	0.071	0.041	0.134**	−0.004	−0.086	0.234**
Olfactory hallucination	−0.020	0.064	0.049	−0.003	0.029	0.266**
Gustatory hallucination	−0.054	0.210*	0.105*	−0.004	0.002	0.169**

Note: R values > 0.3 are bolded.

Abbreviations: A, agreeableness; C, conscientiousness; E, extraversion; FOV, field of vision; N, neuroticism; O, openness; OBE, out of body experience.

^*Statistical significance at p < 0.05.

^**Statistical significance at p < 0.01.

Apart from trait absorption, trait extraversion exhibited the strongest correlations with the intensity of sensory features including gustatory hallucinations (r = 0.210), beautiful visuals (r = 0.192), and colour enhancement (r = 0.141) (Table 2). Trait openness, despite typically being well correlated with trait absorption [35], exhibited relatively few significant correlations, the strongest of which were the intensity of beautiful visuals (r = 0.175) and tactile hallucinations (r = 0.134); it also showed a slight negative association with the intensity of psychoses (r = −0.109). However, it is noted that these correlations are small at best [34].

The three remaining Big Five personality domains exhibited only a few significant correlations, all of which were weak. These included correlations between trait neuroticism and the intensity of disgusting visuals (r = 0.109), trait agreeableness and the intensity of beautiful visuals (r = 0.130), trait conscientiousness and the intensity of colour enhancement (r = 0.159), and trait conscientiousness and the intensity of disgusting visuals (r = −0.144).

Table 3 displays the finalised models from the results of the linear regression analyses. Out of the 20 sensory features examined, 9 produced models with R ² values of 0.1 or greater. For the purposes of brevity, only these 9 are displayed and discussed below.

TABLE 3.

Linear regression models (R ² ≥ 0.1) for the prediction of sensory feature intensity (n = 327).

Dependent	Predictor	B	SE	Final R 2
Trails				0.102
	Social setting (single partner)	0.713**	0.228
	Typical dose	0.380**	0.101
	Absorption	0.036**	0.012
Objects “breathing”				0.126
	Absorption	0.046**	0.011
	Typical dose	0.289**	0.100
	Extraversion	0.035**	0.011
	Agreeableness	−0.043**	0.015
	Physical setting (club)	−0.835*	0.395
Field of vision changes				0.179
	Absorption	0.079**	0.013
	Typical dose	0.448**	0.111
	Social setting (single partner)	0.790**	0.251
Visual acuity changes				0.187
	Absorption	0.087**	0.012
	Intense dosage	0.416**	0.093
Beautiful visuals				0.140
	Absorption	0.043**	0.009
	Extraversion	0.035**	0.009
	Typical dose	0.239**	0.082
	Physical setting (club)	−0.706*	0.324
Taste hallucinations				0.107
	Extraversion	0.044**	0.011
	Absorption	0.033**	0.012
	Age	−0.024**	0.009
Out‐of‐body experiences				0.136
	Absorption	0.084**	0.014
	Intense dosage	0.456**	0.113
Other dimensions/worlds				0.149
	Absorption	0.089**	0.015
	Intense dose	0.508**	0.118
	Physical setting (festival)	0.877*	0.429
Synaesthesia				0.113
	Absorption	0.073**	0.013
	Intense dosage	0.392**	0.100

^*Statistical significance at p < 0.05.

^**Statistical significane at p < 0.01.

The strongest model was produced for the prediction of the typical intensity of visual acuity enhancement F(1,324) = 37.160, p < 0.01, R ² = 0.187 which included the factors of trait absorption (β = 0.087, p < 0.01) and intense dose (β = 0.416, p < 0.01). The next strongest model was for the prediction of typical intensity of FOV changes F(1,323) = 23.492, p < 0.01, R ² = 0.171 which included the trait absorption (β = 0.079, p < 0.01), typical dose (β = 0.448, p < 0.01), and social settings with a single partner (β = 0.790, p < 0.01).

The remaining models show slight declines in R‐Squared values and can be seen in detail in Table 3. Certain models included notable predictor variables: physical settings in night‐clubs were significantly predictive of reduced intensity of objects ‘breathing’ and beautiful visuals (compared to an ‘at home’ setting). Physical settings at festivals were strongly predictive of increased intensity of experiences of other dimensions/worlds. Notably, trait absorption provided a small but significant predictive value to all nine of the discussed models. Trait extraversion was present in three of the nine models, and trait agreeableness in only one. The analyses suggest that traits neuroticism and conscientiousness do not provide unique predictive value for the intensity of the respective subjective features. It is important to note that while personality variables were present in several of the final regression models, beta‐estimates for personality variables were relatively low compared to setting and dosage variables.

4. Discussion

The findings of the current study reveal associations between personality traits and the intensity of several sensory features during the APS. Consistent with the hypothesis, nearly all of the 20 examined sensory features exhibited significant correlations with one or more personality variables, and nine of the features were significantly predicted by models which included personality variables (with R ² ≥ 0.1).

Consistent with previous research, trait absorption was associated with a general increase in the intensity of sensory features. It exhibited associations with 18 of the 20 sensory features, four of which were at least moderate in strength. These findings provide further supporting evidence for the role of trait absorption in sensitivity to altered states of cognition (particularly psychedelics), vivid mental imagery, and its promotive effect on psychedelics as outlined by Haijen et al. [13]. Furthermore, trait absorption was found to be a significant predictor of the intensity of several different sensory features, although this was often in combination with other non‐personality variables. The presence of trait absorption in the final models despite its relatively low strength indicates that it is a significant predictor of various sensory features of the psychedelics experience, albeit in a small way that is not explained by non‐personality variables like dosage and setting.

The observed associations between the Big Five personality traits and the intensity of sensory features were less definitive. None of the Big Five domains exhibited correlation coefficients of moderate or strong strength (r > 0.3); all were weak, if significant. Big Five domains were, however, present in several final regression models with beta‐estimates comparable to those of trait absorption. Several of the findings related to the Big Five domains were unexpected; the lack of significant associations with trait openness was somewhat inconsistent with previous research [6] which highlighted its role as a determinant of acute reactions to psychedelics. It may be that trait openness plays more of a role in determining the cognitive and emotional reactions to psychedelics like the occasioning of MEs [6], rather than the sensory features. Moreover, it is likely that there was substantial crossover between the predictive utility of trait absorption and trait openness, meaning only one was necessary to include in the final model.

Similarly, the associations exhibited by trait extraversion are somewhat inconsistent with previous evidence. In the current study, trait extraversion exhibited the strongest correlations with the intensity of sensory features out of any of the Big Five domains—the strongest being its association with gustatory hallucinations. The overall finding that extraversion is more associated with reactions to psychedelics than other Big Five domains is consistent with findings from Studerus et al. [22]. However, Studerus et al. [22] found that trait extraversion was associated with increased reports of audio‐visual synaesthesia. Whereas in the current study, trait extraversion was not associated with the intensity of synaesthesia nor auditory hallucinations.

Trait neuroticism did not exhibit any predictive value and was correlated with the intensity of very few sensory features. Previous research by Barrett and colleagues [24] examined the associations between trait neuroticism and acute reactions to psychedelic experiences and found associations between trait neuroticism and increased challenging experience under the influence of psychedelics. While the current study only examined sensory features, there was a significant correlation between trait neuroticism and the intensity of disgusting visuals. However, no such association was found for other sensory features linked with challenging experiences such as terrifying visuals, sad visuals or psychoses.

There is little previous evidence linking trait conscientiousness and/or trait agreeableness to acute reactions to psychedelics [23]. Similarly, in the current study, these two domains exhibited very few significant correlations with the intensity of sensory features, and only trait agreeableness was present in any of the final regression models; once again, its beta coefficients were low, and the overall variance explained was low. Interestingly, the observed relationship between trait conscientiousness and the intensity of disgusting visuals is ostensibly inconsistent with the underlying personality theory. Trait conscientiousness is generally associated with disgust sensitivity, with conscientious individuals being more sensitive to feelings of disgust [36]. Yet, in the current study, trait conscientiousness was negatively correlated with the intensity of disgusting visuals. Here, it may be that conscientious individuals are more likely to engage in harm reduction behaviours that facilitate a positive psychedelic experience and thus are less likely to experience negative sensory features such as disgusting visuals. Previous research has found that individuals low in conscientiousness tend to engage in greater risk‐taking behaviours and increased drug use [37].

These findings provide evidence of an association between personality and the intensity of sensory features of the APS. However, they also illustrate that the magnitude of this effect is relatively weak, and that other factors, such as social setting, physical setting and typical dosage, likely play a much stronger role in determining the intensity of acute sensory features and acute reactions to psychedelics in general. Here, it is likely that the effect of personality on the intensity of subjective effects during the APS is a moderating effect more so than a direct effect—with personality variables having an influence on social setting preferences, physical setting preferences, dosage tendencies, harm‐reduction practices, etc. One noteworthy finding here is the prevalence of trait absorption in the final regression models. Its inclusion in all nine of the displayed models attests to its unique and significant contributions to models for the prediction of such sensory effects. As such, it seems appropriate that measures of trait absorption should be considered when constructing tools for the prediction of intensity of certain aspects of the APS.

It is important to consider the limitations present with retrospective self‐report questionnaires. It is likely that several biases influence the participants' response patterns. The most problematic instance of this is any biases stemming from personality traits themselves. For example, it may be that several of the observed associations may stem from the fact that individuals high in certain personality traits are more likely to respond in a certain pattern; individuals high in trait extraversion may be more likely to report a higher intensity of gustatory hallucination, resulting in an observed correlation where no real association is present. Secondly, acquiescence bias or ‘yes’ bias may have been an issue as well; this too could be moderated by personality traits such as trait openness [38]. Thirdly, sampling biases likely occurred to some extent, where individuals high in certain traits (such as trait openness) were more likely to engage in the survey. Fourthly, although the current research collected data on the prevalence of mental disorders in the sample, specific diagnoses were not captured and were not included in any analyses. Future research could examine the interactions between the sensory effects of psychedelics and mental disorders, but this was beyond the scope of this research.

Moreover, it should be acknowledged that, while the current study mainly examined sensory features rather than emotional features of the APS, certain sensory variables had obvious emotional valency. Variables such as ‘beautiful visuals’, ‘terrifying visuals’, and ‘disgusting visuals’ were included in the survey. The rationale behind their inclusion is that during the APS, ostensibly emotional sensory effects may be experienced without a specific emotional reaction. That is, one might experience disgusting visuals without eliciting a reaction of disgust. The obvious emotional valence of these items may skew the role of personality variables observed in the regression models given the direct effect of personality on emotional states. The role of personality variables on the intensity of these distortions during the APS may simply be an effect of personality, unrelated to any interaction with psychedelics.

Furthermore, the necessary assumptions made regarding participants' dosages, and the categorising of dosages into levels from one to five, likely reduced the accuracy of dosage variables and may have contributed to a reduction in their predictive strength during the regression modelling. In the future, participants in similar research should be presented more accurate means of reporting their dosage. Finally, other important determinant information such as the route of administration, participants' mood prior to their experiences, and motivations for use were not collected. These factors are known to influence reactions to psychedelics, and it may be that the usefulness of personality variables as predictors is significantly reduced when these factors are included in regression models for the prediction of acute reactions to psychedelics. Finally, the loss of data from the participants who had used psychedelics on more than 100 occasions likely introduced some bias whereby the findings from the analyses may be less applicable to those with 100 or more psychedelics use occasions.

In conclusion, this study provides evidence of significant associations between personality variables and the intensity of sensory features of the psychedelic experience. However, the strength of the direct correlation is likely weak compared to other extra‐pharmacological factors. It is important to consider the role of personality variables primarily as moderators rather than mediators of the more determinant factors of acute reactions to psychedelics. Nevertheless, the ease with which personality measures can be administered, particularly trait absorption, means they could be efficiently included in measures pertaining to psychedelics. As the scientific and clinical use of psychedelics increases, tools for better prediction of acute reactions to psychedelics will only become increasingly useful to minimise risks and maximise therapeutic benefits.

Author Contributions

Each author certified that their contribution to this work meets the standards of the International Committee of Medical Journal Editors.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Table S1: Ranges used to Inform Coding for Intense and Typical Doses.

Figure S1: Dose Code Frequencies for Participants Typical and Intense Dosages.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.