Psilocybin as a tool for enhancing cognitive flexibility”

INTERVENTION: psilocybin (.17 mg/kg) bodyweight or placebo; Maastricht acute stress test or placebo CONDITION: Neurotransmission, Cognition ; ; PRIMARY OUTCOME: To use psilocybin as a research tool in order to enhance divergent thinking, and facilitate relative goal‐directed versus habitual behaviour during and after drug intoxication, and to assess whether psilocybin will deter a stress induced shift from goal directed to habitual behaviour. SECONDARY OUTCOME: To assess cortical‐subcortical functional connectivity alterations, as well as the relationship between metabolic activity and behavioural outcomes. Furthermore, subjective experience and drug concentration levels will be assessed in relation to the aforementioned variables. INCLUSION CRITERIA: • Previous experience with a psychedelic drug, but not within the past 6 months. • Age between 18 and 40 years • Free from psychotropic medication • Good physical health as determined by medical examination and laboratory analysis • Absence of any major medical, endocrine and neurological condition • Normal weight, body mass index (weight/height2) between 18 and 28 kg/m2 • Proficient knowledge of the English language, defined as having at least 5 years of English language education (in high school or other education) • Written Informed Consent