Edited by: Isadora Olivé, Université Vincennes Saint Denis Paris 8, France
Reviewed by: Philip R. Corlett, Yale University, USA; Matthew W. Johnson, Johns Hopkins University, USA
*Correspondence: Matthew M. Nour
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution and reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Distortions in the subjective experience of one’s “self”, or “ego”, are central to the psychedelic experience (James,
The experience of a compromised sense of self occasioned by psychedelic drugs has been variously called ego-death (Grof,
It is likely that the prior “psychology” of the subject and the environmental setting in which they take a psychedelic influences whether an ego-dissolution experience is welcomed and felt as something positive, or feared and fought against (Eveloff,
Discussions of altered self-experience have been traditionally confined to philosophy or descriptive psychopathology (Stace,
There currently exist several measures that capture feelings related to alterations in self-experience (Strassman et al.,
The primary aim of the present study was to develop and validate the “Ego-Dissolution Inventory” (EDI), a new succinct 8-item self-completed questionnaire designed to operationalize the experience of ego-dissolution so that its construct validity can be tested and developed. In order to do this in an efficient way we chose to utilize online data collection via a large anonymous internet survey. A secondary aim was to investigate the specificity of the relationship between the experience of ego-dissolution and psychedelic drugs, compared with cocaine and alcohol. These two comparator drugs were chosen because of their widespread availability and use in Western societies. Finally, we aimed to test the hypothesis that experiences occasioned by classical stimulant drugs, like cocaine, are in some respects antithetical to the psychedelic experience, promoting ego-inflation rather than ego-dissolution.
Sixteen novel statements relating to the experience of ego-consciousness were included in this study. Eight of these were designed to capture the central phenomenon of ego-dissolution (and the associated feeling of increased union with one’s surroundings, known as dissolved ego-boundaries), and particularly how it has been characterized in the context of the psychedelic experience (Leary et al.,
Item: | Factor 1 Ego-dissolution | Factor 2 Ego-inflation |
---|---|---|
I felt especially assertive | 0.014 | |
−0.040 | ||
I felt more important or special than others | −0.034 | |
0.010 | ||
My ego felt inflated | −0.154 | |
0.167 | ||
I felt especially sure-of-myself | 0.151 | |
−0.066 | ||
I felt especially keen and competitive | −0.134 | |
−0.070 | ||
I felt like my viewpoint was worth more than other peoples’ | −0.075 | |
0.112 | ||
I felt especially self-confident | 0.073 | |
−0.043 | ||
I felt especially self-assured | 0.156 | |
−0.042 |
Each subject was asked to provide information on their age, sex and educational background
691 | ||
238 (34.44%) | ||
Median | 28 | |
Inter-quartile range | 13 | |
Skewness | 1.43 | |
Left school before age 16 (no qualifications) | 2 (0.29%) | |
Left school at 16/GCSE (UK) | 29 (4.20%) | |
High school diploma/A-Level (UK) | 68 (9.84%) | |
Some university (or equivalent) | 168 (24.31%) | |
Bachelor’s degree (or equivalent) | 229 (33.14%) | |
Post-graduate degree (or equivalent) | 195 (28.22%) | |
Never | 107 (15.48%) | 236 (34.15%) |
Once only | 26 (3.76%) | 70 (10.13%) |
2–5 times | 106 (15.34%) | 106 (15.34%) |
6–10 times | 92 (13.31%) | 59 (8.54%) |
11–15 times | 69 (9.99%) | 35 (5.07%) |
16–25 times | 69 (9.99%) | 45 (6.51%) |
26–50 times | 87 (12.59%) | 42 (6.08%) |
51–100 times | 68 (9.84%) | 47 (6.80%) |
>100 times | 67 (9.70%) | 51 (7.38%) |
No alcohol | 191 (27.64%) | |
1–6 units | 213 (30.82%) | |
7–12 units | 123 (17.80%) | |
13–18 units | 58 (8.39%) | |
19–24 units | 38 (5.50%) | |
25–30 units | 19 (2.75%) | |
31–36 units | 17 (2.46%) | |
37–42 units | 8 (1.16%) | |
43–48 units | 7 (1.01%) | |
49–54 units | 6 (0.89%) | |
55–60 units | 4 (0.58%) | |
>60 units | 7 (1.01%) |
After providing these demographic data, subjects were given the opportunity to answer questions on up to four drug experiences: (1) their “most intense” psychedelic experience; (2) a “typical” psychedelic experience; (3) a “typical” cocaine experience; and (4) a “typical” alcohol experience. For psychedelic experiences subjects could further specify the drug taken (options were: LSD, psilocybin, mescaline, DMT and ayahuasca). For each experience subjects were asked to provide information on how long ago the experience was (options were: “Today”, “Last week”, “1–4 weeks” ago, “1–6 months” ago, “6–12 months” ago, “1–5 years” ago, “6–10 years” ago, and “Over 10 years” ago). They were also asked how “intense” the experience was (for psychedelic experiences), or how “energized/wired” or “inebriated/drunk” they felt (for cocaine and alcohol experiences, respectively) on a visual analog scale from 0 to 100, with 0 = “Not at all” and 100 = “The most intense/energized/inebriated imaginable”. The rationale for enquiring about a typical and most intense experience with psychedelics was to collect a greater range of possible responses with regards to psychedelics, which was our primary drug class of interest.
For each experience subjects were also asked to state the dose of the drug taken. For psychedelic drugs, subjects were asked to provide a “rough/ballpark” estimate using an LSD-equivalent dose; available options ranged from “No more than half a tab/50 micrograms of LSD” to “More than 3 tabs/300 micrograms of LSD”, split into 5 non-overlapping groups. This was done with the aim of providing a standard reference against which any non-LSD classical psychedelic could be compared. For cocaine, the dose options available ranged from: “less than 1/8 gram” to “More than 2 grams”, split into six non-overlapping groups. For alcohol, the dose options ranged from: “Less than 3 units” to “Over 24 units”, split into nine non-overlapping groups.
For each drug experience, subjects answered the question “Do you believe that the experience [induced by the relevant drug] and your contemplation of that experience have led to a change in your current sense of personal well-being or life satisfaction?” using a 7-point rating scale (+3 = “increased very much”; +2 = “increased moderately”; +1 = “increased slightly”; 0 = “no change”; −1 = “decreased slightly”; −2 = “decreased moderately”; and −3 = “decreased very much”), taken from the persisting effects questionnaire as per Barrett et al. (
Subjects then answered the 16 ego-consciousness items (Table
The specific MEQ questions included, and their relevant MEQ30 identifiers (Barrett et al.,
This study was approved by the local ethics committee. The survey was implemented and hosted by the online service Survey Gizmo
Participants were recruited to take the online survey via web-link advertisements posted on Facebook groups, Twitter pages, email newsletters, and online drug forums with a short request (“please participate in our anonymous online questionnaire designed to learn more about experiences with classical psychedelics, cocaine, and alcohol”). Recruitment targeted online communities interested in psychoactive substances and altered states of consciousness (e.g., Psychedelic Society
Inclusion criteria for participants were: (1) at least 18 years of age; and (2) had had at least one experience with a classical psychedelic (LSD, psilocybin, DMT, ayahuasca or mescaline), cocaine, and/or alcohol. Data collection occurred over a 4-week period.
We defined a completed form as one in which the subject had answered all 16 ego-consciousness items relating to at least one drug experience, and also provided information about the dose of drug taken, the subjective intensity of the experience, and the effect on well-being.
Scores for the 16 ego-consciousness items for each complete form were subjected to an exploratory factor analysis using the iterated principle axis factor method and an oblique (promax) rotation, which allowed common factors to be correlated (Budaev,
Internal consistency of the scales was assessed with Cronbach’s alpha (Cronbach,
The specificity of the relationship between ego-dissolution and experiences occasioned by classical psychedelics was tested in three ways. Firstly we investigated the correlation between reported drug dose and both ego-dissolution and ego-inflation for each drug class separately (where drug dose was defined as the central value for the selected dose range for each experience). For each drug class the null hypothesis that the dose-ego-dissolution and dose-ego-inflation correlations were equal was tested using a 2-tailed
Secondly, we investigated the relationship between the reported subjective intensity of the experience and ego-dissolution. Correlations between experience intensity and ego-experiences within a drug class were investigated in an identical manner to the dose-response relationships. As ratings of subjective experience intensity are theoretically comparable across drug classes (unlike drug doses) we were able to test the hypothesis that the linear relationship between subjective intensity and ego-dissolution (or ego-inflation) was different between psychedelic, cocaine and alcohol experiences by testing whether the slope of the linear regression line relating subjective intensity (independent variable) to ego-dissolution or ego-inflation (dependent variables) is significantly different between drug classes (using MATLAB’s aoctool [Analysis of covariance (ANCOVA)] function [MATLAB 2015b, Mathworks]).
Finally, a Support Vector Machine (SVM) classifier (a common supervised machine learning algorithm) was trained to distinguish between typical experiences with psychedelics, cocaine and alcohol using only the ego-dissolution and ego-inflation score for each experience, in three binary one-v-one classification tasks (psychedelic vs. cocaine, psychedelics vs. alcohol, cocaine vs. alcohol). Only “typical” psychedelic experiences were included in this analysis to avoid classification problems associated with numerically imbalanced classes (He and Garcia,
The correlation between ego-dissolution or ego-inflation and reported changes in personal well-being was compared both between and within drug classes using Fisher’s
Spearman’s rho was used to quantify all bivariate correlations. Statistical significance is defined as
Six-hundred and ninety-one subjects completed the online survey. Table
To investigate the factor structure of the 16 ego-consciousness items in a hypothesis-free manner, all questions were submitted to an exploratory factor analysis. The Kaiser–Meyer–Olkin measure of sampling adequacy was 0.918 and Bartlett’s test of sphericity was highly significant (χ2(120) = 22441.7,
Both parallel analysis for principle components (Horn,
The data were therefore subjected to an exploratory factor analysis to extract two common factors. Factor 1 comprised of the eight items relating to the experience of “ego-dissolution” whilst Factor 2 comprised of the eight items relating to the experience of “ego-inflation”. Communality values (the proportion of an item’s variance that can be explained by the extracted common factors) ranged from 39% to 82%. Every item loaded strongly and exclusively onto either Factor 1 or Factor 2, demonstrating a simple and easily interpretable factor structure (Table
Guided by the results of the exploratory factor analysis, two 8-item scales were derived, one reflecting the experience of “ego-dissolution”, and one reflecting the experience of “ego-inflation” (Table
For experiences with psychedelic drugs, the score for the MEQ-derived measure of unitive experience correlated strongly with ego-dissolution (rho = 0.735 [95% CI 0.704, 0.763],
For experiences with psychedelic drugs, there was a significant positive correlation between reported drug dose and ego-dissolution (rho = 0.371 [0.317, 0.427],
For experiences with psychedelic drugs, the subjective intensity of the experience was positively correlated with both ego-dissolution (rho = 0.577 [0.529, 0.621],
ANCOVA analysis was used to fit separate regression lines relating subjective intensity (predictor variable) to ego-dissolution or ego-inflation (dependent variables), for each drug class separately. This analysis confirmed that ego-dissolution experiences were significantly predicted by experience intensity (
Ego-inflation experiences were also significantly predicted by subjective intensity (
As a final demonstration of the specificity of the ego-dissolution experience for psychedelic drugs, we trained a SVM binary classifier to distinguish between typical psychedelic (
As a final exploratory analysis, we sought to investigate the relationship between ego-experiences and the extent to which the experience in question changed subjects’ current sense of personal well-being or life satisfaction. For psychedelic drugs, the median response on the 7-point rating scale (with possible answers from −3 to +3) was +2 (+2 = “Increased moderately”, interquartile range = 2, skewness = −0.769, median time elapsed since experience = 1–5 years), which was significantly greater than the median response for cocaine (0 = “No change”, interquartile range = 0, skewness −0.135, median time elapsed since experience = 1–5 years) or alcohol (0 = “No change”, interquartile range = 0, skewness = −0.220, median time elapsed since experience = 1–4 weeks;
There was a trend for a positive correlation between ego-dissolution score and improvement in well-being across all drug classes, with this effect reaching statistical significance after correction for multiple comparisons only for experiences occasioned by psychedelic drugs (psychedelic: rho = 0.392 [0.342, 0.442],
Ego-inflation was positively correlated with improvement in well-being for psychedelic drugs (rho = 0.198 [0.135, 0.263],
For psychedelic experiences, the positive correlation between ego-dissolution and increase in well-being was stronger than between ego-inflation and change in well-being (
The results presented in this study demonstrate the internal consistency, single-factor psychometric structure and construct validity the EDI, a new 8-item self-report questionnaire designed to measure the experience of ego-dissolution. Additionally, our results demonstrate that ego-dissolution positively correlates with drug dose and experience intensity specifically for psychedelic drugs, compared with cocaine or alcohol experiences. This result mirrors the previously demonstrated positive relationship between psilocybin dose and altered states of consciousness, including “oceanic boundlessness” and “dread of ego dissolution” (as measured by the 5D-ASC questionnaire; Hasler et al.,
The experience of a coherent and well-circumscribed self is a cardinal feature of adult human waking consciousness (Carhart-Harris and Friston,
An understanding of the neurobiological correlates of self-experience is also of great importance to a number of mental health conditions, where the sense of self is disrupted or compromised (Northoff,
Our results represent a necessary step in the demonstration of the construct validity of ego-dissolution. Construct validity can be decomposed into discriminant and convergent validity. Discriminant validity of the EDI was demonstrated by the fact that items relating to ego-dissolution and those relating to ego-inflation loaded onto two orthogonal factors in the exploratory factor analysis. Convergent validity of the EDI was demonstrated by the strong positive correlation between EDI and our (MEQ-based) measure of the unitive experience. This suggests that experiences of ego-dissolution, unity and dissolved ego-boundaries may be conceptually inseparable (Federn,
Our measure of ego-inflation, in contrast to ego-dissolution, showed a significant dose-response relationship with cocaine, but not psychedelics or alcohol. Although all three drug classes showed a positive correlation between ego-inflation and experience intensity, this relationship was strongest for cocaine and weakest for psychedelic drugs. These results suggest that experiences occasioned by cocaine are in some sense antithetical to the psychedelic experience; with cocaine seeming to promote self-centeredness rather than the selflessness associated with psychedelics.
Consistent with this hypothesis, a binary SVM classifier was able to identify experiences occasioned by psychedelic drugs vs. cocaine or alcohol with over 85% accuracy using the ego-dissolution and ego-inflation scores alone. This machine-learning approach may be usefully applied in a number of contexts. For example, it may help to inform debates over whether hybrid compounds such as 3,4-methylenedioxymethamphetamine (MDMA) should be classed as “ego-dissolving” psychedelic-like agents, “ego-inflating” stimulant-like agents, both, or neither. Moreover, used in conjunction with neurobiological measures, such as neuroimaging, these tools may help us to identify key (defining) properties of different psychoactive drugs, as well as non-drug-induced states, in a data-driven manner, and may inform novel hypotheses concerning the endogenous role of 5-HT2A receptors. This may help us to address questions regarding the similarities and differences of different altered states of consciousness such as dreaming, psychosis and the psychedelic state (Carhart-Harris,
Subjects in the present study reported that on average their reported experiences with psychedelic drugs had a positive and lasting impact on their well-being, which correlated positively with the degree of ego-dissolution experienced (rho = 0.392). This is consistent with previous work, which has established that mystical (or “peak”) experiences occasioned by psilocybin correlate positively with increases in “openness” (MacLean et al.,
Regarding the neurobiology of the psychedelic state, previous work has indicated that psychedelics disrupt the integrity of the default-mode network (DMN), a normally well-integrated network of (mostly cortical) brain regions that display high metabolic demands, “connector-hub” status and appear to be involved in high-level functions such as the processing of self-specific information (Qin and Northoff,
These previous experimental findings suggest that the integrity of the DMN may be important for normal self-experience (Qin and Northoff,
A recent study found that the degree of ego-dissolution occasioned by LSD was correlated with global functional connectivity (“Functional Connectivity Density”, as measured by functional magnetic resonance imaging (fMRI)) in bilateral temporo-parietal junction (angular gyrus) and bilateral insular cortex (Tagliazucchi et al.,
One limitation of these studies is that they either used a single-item measure of ego-dissolution (Muthukumaraswamy et al.,
The present study has some limitations. Firstly, the population sampled was fairly homogenous, which limits the study’s external validity, and thus our ability to extrapolate to a broader demographic. Specifically, most of our subjects were male, under the age of 30, and had at least some university education. Over half the subjects had used classical psychedelic drugs on over 10 occasions. This also raises the possibility that our subjects’ responses were biased by their familiarity with reports about paradigmatic features of the psychedelic experience, such as ego-dissolution. Moreover, we did not collect information on the setting in which the psychedelic experiences took place, which is known to influence the quality of the experience (Leary et al.,
Given these limitations, future studies should include a more heterogeneous sampling population, perhaps by intentionally recruiting subjects from different cultural and religious backgrounds, to explore the influence of these factors on ego-dissolution. It would also be of interest to investigate the relationship between responses on the EDI and other validated scales, for example the 5D-ASC (Studerus et al.,
In conclusion, the present study offers initial-phase validation of the EDI, and adds to the growing evidence that ego-dissolution is a key phenomenological feature of the psychedelic experience, which may be studied experimentally. The existence of the EDI will facilitate future research into the neural correlates of this experience, which is of relevance for psychedelic-assisted psychotherapy and the phenomenology of certain psychiatric conditions.
MMN and RLC-H conceived of and designed this study and interpreted the results; contributed to drafting the work and revised it critically for important intellectual content. All authors approved the final version of this manuscript to be published and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work be appropriately investigated and resolved. MMN and LE undertook statistical analysis of the data. LE managed the implementation of the questionnaire and subsequent data collection. MMN wrote the article, with editing from RLC-H.
MMN is funded by the Medical Research Council, UK. RLC-H is funded by Mosley Foundation. DN is funded by Safra Foundation.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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