University of Sussex

File(s) not publicly available

Assessing expectancy and suggestibility in a trial of escitalopram v. psilocybin for depression

journal contribution
posted on 2024-04-03, 13:07 authored by Balázs Szigeti, Brandon Weiss, Fernando Ernesto Rosas De AndracaFernando Ernesto Rosas De Andraca, David Erritzoe, David Nutt, Robin Carhart-Harris


To investigate the association between pre-trial expectancy, suggestibility, and response to treatment in a trial of escitalopram and investigational drug, COMP360, psilocybin, in the treatment of major depressive disorder ( registration: NCT03429075).


We used data (n = 55) from our recent double-blind, parallel-group, randomized head-to-head comparison trial of escitalopram and investigational drug, COMP360, psilocybin. Mixed linear models were used to investigate the association between pre-treatment efficacy-related expectations, as well as baseline trait suggestibility and absorption, and therapeutic response to both escitalopram and COMP360 psilocybin.


Patients had significantly higher expectancy for psilocybin relative to escitalopram; however, expectancy for escitalopram was associated with improved therapeutic outcomes to escitalopram, expectancy for psilocybin was not predictive of response to psilocybin. Separately, we found that pre-treatment trait suggestibility was associated with therapeutic response in the psilocybin arm, but not in the escitalopram arm.


Overall, our results suggest that psychedelic therapy may be less vulnerable to expectancy biases than previously suspected. The relationship between baseline trait suggestibility and response to psilocybin therapy implies that highly suggestible individuals may be primed for response to this treatment.


Publication status

  • Published


Psychological Medicine




Cambridge University Press (CUP)

Page range


Department affiliated with

  • Informatics Publications


University of Sussex

Peer reviewed?

  • Yes