This study will recruit healthy volunteers who use cannabis infrequently. Each participant will attend the laboratory on five occasions: an initial visit to check that they are safe to join the study and four days of testing.

Participants will be administered, in a randomized order, vaporized cannabis containing one of four different ratios of CBD:THC (0:1, 1:1, 2:1, 3:1). The cannabis administration will follow a standardised inhalation procedure using a medical-grade vaporizer device.

Participants will complete a series of tasks measuring cognition, psychosis, anxiety and other subjective experiences.

The study will be carried out at the NIHR-Wellcome Trust Clinical Research Facility at King's College Hospital.

Inclusion Criteria:

• Female and male volunteers aged 21-50
• Have used cannabis at least once
• Willing to provide written informed consent
• Willing to provide blood samples
• Fluent English speaker

Exclusion Criteria:

• Past or present major mental illness
• Past or present major physical illness
• Past or present substance use disorder
• Past or present use of anti-psychotic or anti-depressant medications
• First degree relative with psychotic disorder
• Currently taking psychotropic medication
• Positive urine drug screen at screening or experimental visits
• Use of alcohol 24h prior to experimental visit or tobacco on the day of experiment
• Pregnancy (current or planned) or lactation in women
• Significant abnormality detected during physical examination at screening visit
• Cannabis use (defined as days in which cannabis is used recreationally) more than once per week on average over the last 12 months
• Any past use of synthetic cannabinoids
• Score of 5 and above on the Fagerstrom Nicotine dependence questionnaire
• BMI classified as obese or underweight
• Taken part in any drug study within the last 30 days or taking part in another study over the course of the trial
• Known drug sensitivity/allergy towards cannabis or Lorazepam