The goal of this study is to assess the effects of LSD on neural synchrony, prosocial behavior, and relationship quality in healthy romantic couples.
Evidence is growing that psychedelic substances such as psilocybin, lysergic acid diethylamide (LSD) and ayahuasca could be a potential alternative treatment option for common and difficult to treat psychiatric conditions. One proposed mechanism that psychedelics target, which is a hallmark of seemingly all psychiatric disorders, are deficits in social cognitive abilities. However, the neural underpinnings of psychedelic induced alterations in prosocial behavior are currently unknown. The investigators hypothesize psychedelics increase such prosocial behaviors by increasing neural synchrony, which is the coupling of brain-to-brain activity across two or more people; it has been found to underlie social connection and various forms of shared prosocial behavior. The current project will primarily assess whether LSD enhances neural synchrony between romantic partners. Second, the investigators will assess whether LSD enhances prosocial behavior between members of a dyad, thus replicating previous studies which assessed prosocial behavior within one individual at a time. The investigators will also assess the relationship between neural synchrony and outcome variables of the prosocial behaviour tasks. Lastly, it will be assessed whether LSD-induced changes in neural synchrony and/or prosocial behaviour affect persisting relationship quality. Oxytocin and cytokine concentrations, will also be quantified to investigate whether there is a relationship between these factors and changes in prosocial behaviour. The study design will be conducted according to a double-blind, placebo-controlled, 2-way crossover design. Healthy participants (N=60) who are in a relationship (N=30 couples) will receive placebo and an oral dose of 50 µg of LSD. Between each condition, there will be a minimum of 14 days washout. This leads to a total study duration of minimally four weeks, for a participant to go through the medical examination and both drug conditions.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
DOUBLE
Enrollment
60
Maastricht University
Maastricht, Netherlands
RECRUITINGNeural synchrony
Quantification of neural synchrony between members of a couple utilizing previously validated naturalistic interaction paradigms, including a motor cooperation task, empathy giving task, and affective touch and eye contact paradigm, will be employed. Resting state EEG will be used as a control.
Time frame: On the acute dosing test day, 1.5-2 hours after substance administration
Empathy
Cognitive and emotional empathy will be assessed via the empathy giving task (EGT) and the multifaceted empathy test (MET).
Time frame: On the acute dosing test day, 2 hours (EGT) and 3 hours (MET) after substance administration
Self-other distinction
The degree of self-other merging will be assessed using synchronous multisensory stimulation (SMS), and responses on the inclusion of other in the self scale (OIS).
Time frame: On the acute dosing day, 2.5 hours (SMS) after substance administration. The OIS will be administered repeatedly at baseline (-0.5 hours), 2 hours, 3 hours, 4.5 hours, and 7 hours after substance administration, and at 2 days follow up.
Prosocial behavior
Prosocial behavior will be assessed via participants' response rate on the prosocial learning task (PLT), and the amount of effort for other individual in the prosocial effort task (PET).
Time frame: On the acute dosing day, 6 hours after substance administration. The PET will also be administered at 2 days follow-up.
Social influence processing
Social influence processing will be assessed via participants' degree of rating adjustment after feedback in the social influence paradigm (SIP).
Time frame: On the acute dosing day, 3 hours after substance administration
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Trust
The trust game for couples (TGC) will assess participants' willingness to invest personal resources in pro-relationship attitudes.
Time frame: On the acute dosing day, 6.5 hours after substance administration
Creativity
Creativity will be assessed by the semantic distance in the chain free association (CFO) and the divergent association tasks (DAT), and also by the ability to separate old and new information in the pattern separation task (PST).
Time frame: On the acute dosing day, 5.5 hours (CFO, PST) after substance administration. The DAT will be administered at 2 days follow-up.
Sociality
Sociality will be measured by the social reward questionnaire (SRQ) and the visual analogue scales that measure feelings of social behavior (VAS-S).
Time frame: On the acute dosing day, SRQ will be administered at 4.5 hours after substance administration, while the VAS-S will be administered at baseline (-0.5 hours), at 1, 2, 3, 4, 5, 6, and 7 hours after substance administration.
Conflict resolution
The couples conflict resolution (CR) task will measure the duration of positive and negative behavior of members of a couple via video recordings of couples' interactions.
Time frame: At 2 days follow-up.