Acute subjective effects after smoking joints containing up to 69 mg Δ9-tetrahydrocannabinol in recreational users: a randomized, crossover clinical trial

Psychopharmacology (Berl). 2014 Dec;231(24):4723-33. doi: 10.1007/s00213-014-3630-2. Epub 2014 May 31.


Rationale: An increase in the potency of the cannabis cigarettes has been observed over the past three decades.

Objectives: 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Affect / drug effects*
  • Attention / drug effects*
  • Blood Pressure / drug effects
  • Cannabinoids / administration & dosage*
  • Cannabinoids / blood
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Dronabinol / administration & dosage*
  • Dronabinol / blood
  • Heart Rate / drug effects
  • Humans
  • Male
  • Marijuana Smoking / blood
  • Marijuana Smoking / psychology*
  • Middle Aged
  • Psychomotor Performance / drug effects*
  • Time Factors
  • Young Adult


  • Cannabinoids
  • Dronabinol