The role of alcohol in expectancy-driven mystical experiences: a pre-registered field study using placebo brain stimulation

Figures & data

Table 1. Inter-rater reliability scores and average number of occurrences of the categorization scheme categories.

	κ	N	%
Auditory	0.87	30.3	16.1
Visual	1	27.5	14.6
Mental	0.74	24	12.8
Weak bodily sensations	0.87	147.5	78.5
Strong bodily sensations	0.67	56.5	30.1
Events in surrounding	0.78	38.5	20.5
Time/space distortion	0.78	10.5	5.6
Distraction/skepticism	0.81	57	30.3

Note: κ = Cohen’s Kappa; N = the average number of occurrences for the two raters; % = the average number of occurrences expressed in percentages; N/188.

Table 2. Categorization scheme with frequency of occurrences per category and sub-category.

Category	Sub-category	N	%
Auditory	1. Agent voices	21.5	11.9
	2. Music/melody	17.5	9.7
	3. Other sounds	15.5	8.6
Visual	1. Flashes/light/light at end of tunnel	13	7.2
	2. Imagery/visuals/objects	22.5	12.5
	3. Agents/people/shadows	14	7.8
Mental	1. Feelings/emotions	5	2.8
	2. Self-referential processing	6	3.4
	3. Mind-wandering	4	2.2
	4. Memories of past drug experiences	9	5.0
Weak bodily sensation	1. Cold/shivering/goosebumps	7	3.9
	2. Itch/tingling/light pain	41	22.8
	3. Stress/heart rate increase/hot/sweat	29	16.1
	4. Light touches	10.5	5.8
	5. Dizziness	22.5	12.5
	6. Sleepiness/relaxation	37.5	20.8
Strong bodily sensation	1. Involuntary movements	18	10.0
	2. Out-of-body/floating	15.5	8.6
	3. Ego dissolution	6.5	3.6
	4. Paralyzed	4	2.2
	5. Heavy arms/legs/head	12.5	6.9
Events in surrounding	1. Feeling of a presence	10	5.6
	2. Moving surroundings	8	4.4
	3. Forces	20.5	11.4
Time/space distortion	1. Time distortion	3.5	1.9
	2. Space distortion	4	2.2
	3. Feeling of oneness	3	1.7
Distraction/ skepticism	1. Distraction	25	13.9
	2. Doubts about helmet	9.5	5.3
	3. Felt bored	5.5	3.1
	4. Nothing happened	17	9.4

Note: N = the average number of occurrences for the two raters; % = the average number of occurrences expressed in percentages; N/188.

Table 3. Correlation table for the relationship between alcohol and response inhibition performance of the Stroop Task.

	1. Alc obj	2. Alc subj1	3. Alc subj2	4. RI
	(N = 193)	(n = 138)	(n = 138)	(n = 187)
1.	–	.58*** (n = 138)	.43*** (n = 138)	−.18* (n = 187)
2.		–	.27** (n = 138)	.09 (n = 138)
3.			–	−.20* (n = 138)
4.				–

Note: * p < .05, ** p < .01, ***p < .001; Correlations represent Pearson correlations; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter (range = 0–2); Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition.

Table 4. Descriptive statistics of the measures included in the regression models.

	Frequency	Intensity S	Intensity M	Alc obj	Alc subj1	Alc subj2
N	196	193	193	193	138	138
M	4.1	20.3	1.5	0.30	3.9	17.4
SD	7.8	25.3	1.7	0.34	3.4	20.0

Table 4. Continued.

	RI	Religiosity	Spirituality	Parents
N	192	193	193	193
M	176.6	15.2	39.4	37.1
SD	595.0	20.3	26.7	28.9

Note: N = number of cases; M = mean; SD = standard deviation; Frequency = frequency of extraordinary experiences; Intensity S = intensity of the extraordinary experiences as measured with the single mystical intensity slider (range = 0–100); Intensity M = average score on the mysticism scale items (range = 0–8); Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter (range = 0–2); Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition; Parents = religiosity/spirituality of the parents (range = 0–100).

Table 5. Generalized linear models for predicting the frequency of extraordinary experiences.

GzLM1	b	SE b	p	GzLM2	b	SE b	p
Constant	2.16	0.53	<.001***	Constant	2.25	0.71	.002**
Gender2	0.07	0.25	.778	Gender2	0.01	0.30	.979
Age	−0.03	0.02	.056	Age	−0.04	0.02	.047*
Alcohol obj	−0.03	0.36	.929	Alcohol obj	0.12	0.59	.845
Education2	−0.86	0.35	.014*	Education2	−1.30	0.44	.003**
Education3	−0.54	0.34	.113	Education3	−0.80	0.43	.064
Education4	0.43	0.67	.522	Education4	0.49	0.77	.524
Religiosity	0.01	0.01	.170	Religiosity	0.01	0.01	.389
Spirituality	0.01	0.01	.034*	Spirituality	<.01	0.01	.409
Parents	<.01	<.01	.529	Parents	0.01	0.01	.131
RI	<.01	<.01	.250	RI	<.01	<.01	.887
				Alc subj1	0.01	0.05	.257
				Alc subj2	0.01	0.01	.261

Note: *p < .05, **p < .01, ***p < .001; GzLM1 = generalized linear model without the retrospective data (N = 196); GzLM2 = generalized linear model including the retrospective data (N = 132). The dependent variable is the frequency with which participants responded on the button press task. Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Parents = extent to which the parents are religious/spiritual; RI = response inhibition score obtained with the Stroop Task; Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74).

Table 6. Hierarchical linear regression models for predicting the intensity of extraordinary experiences.

	b	SE B	β	p
HLR 1
Step 1
Constant	0.03	0.16		.863
	[−0.29/0.35]
Gender	0.05	0.07	.06	.448
	[−.08/.18]
Age	−0.01	<0.01	−.13	.075
	[−.02/<.01]
Education	−0.05	0.04	−.09	.212
	[−0.13/0.03]
Step 2
Constant	−0.07	0.17		.690
	[−0.40/0.26]
Gender	0.01	0.07	.01	.862
	[−0.12/0.15]
Age	−0.01	0.01	−.17	.021*
	[−0.02/0.00]
Education	−0.03	0.04	−.06	.419
	[−0.11/0.05]
Religiosity	<0.01	<0.01	.04	.630
	[<0.01/0.00]
Spirituality	0.01	<0.01	.27	.001**
	[<0.01/0.01]
Parents	<−0.01	<0.01	−.08	.340
	[<0.01/<0.01]
Alcohol	0.06	0.10	.05	.525.
	[−0.13/0.25]
RI	<0.01	<0.01	−.02	.772
	[<0.01/<0.01]
HLR 2
Step 1
Constant	0.14	0.21		.502
	[−0.25/0.54]
Gender	0.03	0.08	.03	.696
	[−0.02/0.00]
Age	−0.01	0.01	−.16	.074
	[−0.12/0.17]
Education	−0.07	0.05	−.12	.174
	[−0.15/0.03]
Step 2
Constant	−0.11	0.22		.639
	[−0.52/0.36]
Gender	<0.01	0.10	−.01	.961
	[−0.02/<0.01]
Age	−0.01	0.01	−.14	.101
	[−0.16/0.14]
Education	−0.05	0.05	−.10	.279
	[−0.14/0.03]
Religiosity	<0.01	<0.01	.10	.301
	[<0.01/0.01]
Spirituality	0.01	<0.01	.21	.032*
	[<0.01/0.01]
Parents	<0.01	<0.01	−.02	.845
	[<0.01/<0.01]
Alc obj	−0.01	0.16	−.07	.564
	[−0.39/0.17]
Alc subj1	0.01	0.01	.11	.269
	[−0.01/0.03]
Alc subj2	<0.01	<0.01	.16	.132
	[<0.01/0.01]
RI	<0.01	<0.01	−.05	.550
	[<0.01/<0.01]

Note: * p < .05, ** p < .01; 95% CI between brackets; HLR1 = hierarchical linear regression model without the retrospective data (N = 193); HLR2 = hierarchical linear regression model including the retrospective data (N = 132). The dependent variable is the result of the log transformation of the regression weights of the principal component factor analysis conducted on the intensity scale and the mystical scale items. Parents = extent to which the parents are religious/spiritual; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition.