title: Acute subjective effects after smoking joints containing up to 69 mg Δ9-tetrahydrocannabinol in recreational users: a randomized, crossover clinical trial.
abstract: BACKGROUND
  An increase in the potency of the cannabis cigarettes has been observed over the past three decades.
  
  
  OBJECTIVE
  In this study, we aimed to establish the impact of Δ9-tetrahydrocannabinol (THC) on the rating of subjective effects (intensity and duration of the effects), up to 23 % THC potency (69 mg THC) among recreational users.
  
  
  METHODS
  Recreational users (N = 24) smoked cannabis cigarettes with four doses of THC (placebo 29, 49 and 69 mg of THC) on four separate test days in a randomized, double-blind, placebo-controlled, crossover study. The participants filled in three different questionnaires measuring subjective effects during the exposure up to 8 h post-smoking. The 'high' feeling, heart rate, blood pressure and THC serum concentrations were also regularly recorded during these 8 h.
  
  
  RESULTS
  THC significantly increased the high feeling, dizziness, dry-mouthed feeling, palpitations, impaired memory and concentration, and 'down', 'sedated' and 'anxious' feelings. In addition, THC significantly decreased alertness, contentment and calmness. A cubic relationship was observed between 'feeling the drug' and 'wanting more'. The THC-induced decrease in 'feeling stimulated' and increase in anxiety lasted up to 8 h post-smoking. Sedation at 8 h post-smoking was increased by a factor of 5.7 with the highest THC dose, compared to the placebo.
  
  
  CONCLUSIONS
  This study shows a strong effect of cannabis containing high percentages of THC on the rating of subjective effects. Regular users and forensic toxicologists should be aware that the THC-induced increase in 'feeling sedated' continues longer with a 69 mg THC dose than with a 29 mg THC dose.
authors.affiliation: National Dutch Poisons Information Center, University Medical Center Utrecht, PO Box 85500, 3508, GA, Utrecht, The Netherlands, c.hunault@umcutrecht.nl.
authors.forename: Claudine C
authors.initials: CC
authors.lastname: Hunault
authors.forename: Koen B E
authors.initials: KB
authors.lastname: Böcker
authors.forename: R K
authors.initials: RK
authors.lastname: Stellato
authors.forename: J Leon
authors.initials: JL
authors.lastname: Kenemans
authors.forename: Irma
authors.initials: I
authors.lastname: de Vries
authors.forename: Jan
authors.initials: J
authors.lastname: Meulenbelt
mesh_terms: D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects*; D001288:Attention / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D002186:Cannabinoids / Q000008:administration & dosage* / Q000097:blood; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D013759:Dronabinol / Q000008:administration & dosage* / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000097:blood / Q000523:psychology*; D008875:Middle Aged; D011597:Psychomotor Performance / Q000187:drug effects*; D013997:Time Factors; D055815:Young Adult
chemical_list: D002186:Cannabinoids; D013759:Dronabinol