Background: Due to increasing evidence of efficacy in treating mental health disorders, psilocybin may become a legal medicinal drug. This study tested the validity of Carhart-Harris & Nutt (2017) model of extra-pharmacological (EP) factors and examined whether such factors should be taken into account in any psychological suitability test for medicinally prescribed psilocybin.

Method: 219 participants (101 self-identified females, 109 males, 7 non-binary people and 2 who preferred not to say), with an age range of 18 to 68, completed three online measures of ‘personality’; ‘set, setting and intention’, and the ‘Attitudes Towards Psilocybin’ (ATP) scale. The sample was equally divided between those who had used psychedelics (52.1%) and those who had no previous psychedelic use (47.5%). A series of stepwise linear regressions were run to examine of extra-pharmcological factor predictors of ATP.

Results: The ATP scale was tested in terms of its reliability, construct validity, determinant validity and was deemed an appropriate measure. A model consisting of Set, Openness to Experience and Extraversion significantly predicted ATP scores.

Conclusion: These findings supported the EP model and suggest that a suitability test may be a useful tool when determining whether a prescription of psilocybin is an appropriate course of treatment.