The study looks into whether administering psychedelic substances that stimulate the serotonin system influences pro-social behavior when compared to administering substances that stimulate the dopamine system in healthy individuals.
Psychedelic substances have been shown to be powerful modulators of social perception and behavior during the acute experience. This is of particular interest given that social relationships play a key role in the development and resolution of psychiatric symptoms. However, the neuropharmacological mechanism underlying pro-social effects and time-dependent changes currently remain unclear. This study therefore aims at answering two key questions: 1) Does stimulation of the serotonin system induce lasting effects on pro-social behavior? and 2) Are these effects specific to serotonergic stimulation? The following proposed study will assess these questions by investigating objective, ecologically valid measures of pro-social cognition four weeks after different pharmacological challenges (MDMA, an entactogen and releaser of serotonin, norepinephrine, and dopamine; psilocybin: a classical psychedelic and serotonin 2A receptor agonist, methylphenidate: an amphetamine and norepinephrine-dopamine re-uptake inhibitor) in healthy volunteers.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
122
Single dose of psilocybin (15mg), orally in form of capsules
Single dose of MDMA (100mg), orally in form of capsules
Single dose of methylphenidate (60mg), orally in form of capsules
Psychiatrische Universitätsklinik Zürich
Zurich, Canton of Zurich, Switzerland
Multifaceted Empathy Test
The Multifaceted Empathy Test is a task assessing the cognitive and emotional aspects of empathy. Participants process 40 photos of people in emotionally charged situations. Each aspect of empathy (implicit and explicit emotional empathy, and cognitive empathy) is tested with 20 positive valence stimuli and 20 negative valence stimuli, yielding a total of 120 trials.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Moral Inference Task
The Moral Inference task is an approach to evaluate the computational basis of moral inference and its temporal dynamics. Participants observe and predict the decisions of two "agents" who repeatedly choose on administering painful electric shocks to another person in a different room in return for money, and rate them every third trial for their moral character. At the end of the game there is a short trust game. Participants can win actual money in this game (up to 1 CHF).
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Zurich Prosocial Game
The Zurich Prosocial Game is a computer-based pro-social game which allows for assessment of prosocial behavior, considering the influence of helping cost, distress cues in helping behavior, and reciprocity on pro-social behavior through different trial types. Participants can win actual money in this game (up to 6.50 CHF).
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Social Gaze Task
The Social Gaze Task is a paradigm in which participants' gaze is used to control the gaze of a tropomorphic virtual figure. The aim is to capture the reciprocal and interactive nature of joint attention. Participants' gaze behavior is recorded using an eye-tracking device. The outcome measures we will use are pupil size, valence, and arousal ratings.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
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Moral Expansion Task
In the Moral Expansion Task, the influence of social distance is elicited by having participants indicate countries with different social distances and decide how much money out of CHF 100 they would like to donate to the Red Cross in each country. One participant's choice is then randomly selected, and the donation is implemented while the chosen participant receives the remaining amount.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Social Network Questionnaire
The Social Network Questionnaire is used to assess the size of a person's social network and the emotional support and strain experienced from that network. Participants provide the initials of personal contacts from various domains with whom they have had contact with in the past 4 weeks. 28 items are rated on a 6-point scale, asking how much emotional support and emotional burden they have felt from their social contacts. The total score for those items ranges from 28 to 168.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Pro-social Voting Behavior
The Pro-social Voting Behavior is used to evaluate pro-social voting behavior as a real-world measure of social behavior. The scale consists of 11 items. Each item is rated on a 4-point scale. The total score ranges from 11 to 44. Not all items are accounted equally to capture pro-social voting behavior, as some are reversed.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Oxford Utilitarianism Scale
The Oxford Utilitarianism Scale measures two dimensions of utilitarian tendencies. The scale consists of 9 items. Each item is rated on a 7-point scale. The total score ranges from 9 to 63.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Compassion Scale
The Compassion Scale measures an individual's level of compassion towards others. The scale consists of 16 items. Each item is rated on a 5-point scale. The total score ranges from 16 to 80.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
Inclusion of others in the self
The Inclusion of others in the self is designed to assess the perceived relationship between an individual's self and other people/all living things. It consists of two items. Each item is rated as circles corresponding to a numerical score, ranging from 1 to 8. The total score ranges from 2 to 16.
Time frame: t0 - 10 days (+/- 7 days), t0, and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration
5-Dimensional Altered States of Consciousness Rating Scale
The 5-Dimensional Altered States of Consciousness Rating Scale measures subjective experiences of altered states of consciousness. It contains 94 items, which are formulated as a visual analog scale, assessing different dimensions of altered states of consciousness.
Time frame: t0 (the day of substance administration)
5-Dimensional Altered States of Consciousness Rating Scale short
The 5-Dimensional Altered States of Consciousness Rating Scale short is a shorter version of the 5-Dimensional Altered States of Consciousness Rating Scale for measuring subjective experiences of altered states of consciousness. The scale consists of 15 items chosen from the full version, which are formulated as a visual analog scale.
Time frame: t0 (the day of substance administration)
Mystical Experience Questionnaire
The Mystical Experience Questionnaire is used to assess mystical experiences. The scale consists of 30 items. Each item is rated on a 6-point scale (from 0 to 5). The total score ranges from 0 to 150.
Time frame: t0 (the day of substance administration)
Persisting Effects Questionnaire
The Persisting Effects Questionnaire is used to assess changes in attitudes, moods, behavior, and spiritual experience. The scale consists of 144 items. 140 items are rated on a 6-point scale (from 0 to 5). The last four items use different scaling. The total score ranges from 4 to 724.
Time frame: t0 + 4 weeks (+/- 3 days) and t0 + 16 weeks (+/- 7 days); t0 being the day of substance administration
Epistemic and personal transformation (pre and post versions)
The Epistemic and personal transformation is used to capture the intensity and qualities of epistemic and personal transformation and participants' expectations and desires thereof. Both pre and post versions include open questions and 4 items that are rated on a visual analog scale from 0 to 100. The total score ranges from 0 to 400 for pre and post versions each. The post version additionally captures the substance intake assumption of the participants.
Time frame: t0 (the day of substance administration)
Symptom Checklist 90-R
The Symptom Checklist 90-R is used to assess a broad range of psychological problems and symptoms of psychopathology within the past seven days. It consists of 90 items. Each item is rated on a 5-point scale (from 0 to 4). The total score ranges from 0 to 360.
Time frame: t0 - 10 days (+/- 7 days) and t0 + 16 weeks (+/- 7 days); t0 being the day of substance administration
The Positive and Negative Affect Schedule
The Positive and Negative Affect Schedule is used to assess both positive and negative affect. It consists of two 10-item scales, one measuring positive affect and one measuring negative affect. Each item is rated on a 5-point scale (from 0 to 4). The total scores range from 0 to 80.
Time frame: t0 - 10 days (+/- 7 days), t0, t0 + 4 weeks (+/- 3 days), and t0 + 16 weeks (+/- 7 days); t0 being the day of substance administration
FEELINGS
The FEELINGS scales consist of a series of six short questionnaires to assess regulation, self-esteem, satisfaction with life, life orientation, and meaning in life. Emotional Regulation Questionnaire uses a 7-point scale with a total score range from 7 to 70 (10 items). Satisfaction with Life Scale uses a 7-point scale with a total score range from 5 to 35 (5 items). Rosenberg Self-Esteem Scale uses a 4-point scale with a total score range from 10 to 40 (10 items). Life Orientation Test-Revised uses a 5-point scale with a total score range from 10 to 50 (10 items). Lebenssinn-Fragebogen uses a 7-point scale with a total score range from 10 to 70 (10 items). HSF uses a 5-point scale with a total score range from 6 to 30 (6 items).
Time frame: t0 - 10 days (+/- 7 days) and t0 + 16 weeks (+/- 7 days); t0 being the day of substance administration
Ego Consciousness Change of Perspective Questionnaire (1 & 2)
Ego Consciousness Change of Perspective Questionnaire is used to measure the two dimensions Consciousness and Ego. Questions for the acute effects of substance intake (27 items) and questions for the longer-lasting effects (6 items) are included. Each item is rated on a visual analog scale from 0 to 100. The total score ranges from 0 to 3300.
Time frame: t0 and t0 + 4 weeks (+/- 3 days); t0 being the day of substance administration