LSD Occupancy of the Serotonin 2A Receptor in the Human Brain

Inclusion Criteria:

• Healthy individual between 18-75 years old

Exclusion Criteria:

* Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification)
* Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification) in a first degree relative (i.e., parents, siblings)
* Current or past history of neurological disease, significant somatic condition/disease
* Use of medication that could potentially influence results (e.g.., drugs that act on relevant components of the serotonin system or may interfere with metabolism of study drug)
* Non-fluent Danish language skills
* Profound visual or auditory impairments
* Severe learning disability
* Pregnancy on the scan date, verified by a pregnancy test (test omitted if confirmed that individual is post-menopausal)
* Lactation (females)
* Contraindications for magnetic resonance imaging (e.g., pacemaker, claustrophobia, etc.)
* Contraindications for positron emission tomography
* Alcohol or drug abuse
* Allergy to administered compounds
* Participant in research study with \>10 millisievert exposure within the past year or significant occupational exposure to radioactive substances
* Abnormal ECG (ECG indicating current or previous heart disease or predisposition to heart disease, e.g., QT prolongation) or use of QT prolonging medication
* Use of psychedelic substance within the preceding six months
* Blood donation up to three months before the study (i.e., more than 500ml of blood)
* Head injury or concussion resulting in loss of consciousness for more than 2 min
* Haemoglobin levels \< 7.8 mmol/l for women and 8.4 mmol/l for men
* Ferritin levels outside normal range (12-300 µg/L)
* Body-weight \< 50 kg or \> 110kg
* body-mass index \> 35
* Individual assessment by research staff deeming drug administration unsafe due to ethical or psychological circumstance of the participant