From Relaxed Beliefs Under Psychedelics (REBUS) to Revised Beliefs After Psychedelics (REBAS): Preliminary Development of the RElaxed Beliefs Questionnaire (REB-Q)

The Relaxed Beliefs Under pSychedelics (REBUS) model suggests that psychedelics reduce the strength of deeply held beliefs. In a preliminary test of this idea, 11 healthy adults received a low (1 mg) and a high (25 mg) dose of psilocybin four weeks apart. Confidence in negative self-beliefs decreased after the high dose but not after the low dose. Greater brain signal entropy and stronger subjective effects during the high dose correlated with larger decreases in negative belief confidence, both during the session and four weeks later. Reduced confidence in negative beliefs was strongly linked to improved well-being at the four-week follow-up. These findings provide initial psychological support for the REBUS model, though replication in larger and clinical samples is needed.

Study at a glance

Abstract

Background: The Relaxed Beliefs Under pSychedelics (REBUS) model proposes that serotonergic psychedelics decrease the precision weighting of neurobiologically-encoded beliefs, and offers a unified account of the acute and therapeutic action of psychedelics. Although REBUS has received some neuroscientific support, little research has examined its psychological validity. We conducted a preliminary examination of two psychological assumptions of REBUS: (a) psychedelics foster acute relaxation and post-acute revision of confidence in mental-health-relevant beliefs; (b) this relaxation and revision facilitates positive therapeutic outcomes and is associated with the entropy of EEG signals (an index of neurophysiological mechanisms relevant to REBUS). Method: Healthy individuals (N=11) were administered 1 mg and 25 mg psilocybin 4-weeks apart. Confidence ratings for personally held negative and positive beliefs were obtained before, during, and 4-weeks after dosing sessions. Acute entropy and self-reported subjective experiences were measured, as was well-being (before and 4-weeks after dosing sessions). Results: Confidence in negative self-beliefs decreased following 25 mg psilocybin and not following 1 mg psilocybin. Entropy and subjective effects under 25 mg psilocybin correlated with decreases in negative self-belief confidence (acute and 4-weeks after dosing). Particularly strong evidence was seen for a relationship between decreases in negative self-belief confidence and increases in well-being at 4-weeks. Conclusions: We report the first empirical evidence that the relaxation and revision of negative self-belief confidence mediates positive psychological outcomes; a psychological assumption of REBUS. Replication within larger and clinical samples remains necessary. We also introduce a new measure, the Relaxed BEliefs Questionnaire (REB-Q), for examining the robustness of these preliminary findings and the utility of the REBUS model.