Cognitive and subjective dose-response effects of acute oral Delta 9-tetrahydrocannabinol (THC) in infrequent cannabis users

Psychopharmacology (Berl). 2002 Oct;164(1):61-70. doi: 10.1007/s00213-002-1169-0. Epub 2002 Jul 23.


Rationale: Although some aspects of memory functions are known to be acutely impaired by delta(9)-tetrahydrocannabinol (delta(9)-THC; the main active constituent of marijuana), effects on other aspects of memory are not known and the time course of functional impairments is unclear.

Objective: The present study aimed to detail the acute and residual cognitive effects of delta(9)-THC in infrequent cannabis users.

Methods: A balanced, double-blind cross-over design was used to compare the effects of 7.5 mg and 15 mg delta(9)-THC with matched placebo in 15 male volunteers. Participants were assessed pre and 1, 2, 4, 6, 8, 24 and 48 h post-drug.

Results: Delta(9)-THC 15 mg impaired performance on two explicit memory tasks at the time of peak plasma concentration (2 h post-drug). At the same time point, performance on an implicit memory task was preserved intact. The higher dose of delta(9)-THC resulted in no learning whatsoever occurring over a three-trial selective reminding task at 2 h. Working memory was generally unaffected by delta(9)-THC. In several tasks, delta(9)-THC increased both speed and error rates, reflecting "riskier" speed-accuracy trade-offs. Subjective effects were also most marked at 2 h but often persisted longer, with participants rating themselves as "stoned" for 8 h. Participants experienced a strong drug effect, liked this effect and, until 4 h, wanted more oral delta(9)-THC. No effects of delta(9)-THC were found 24 or 48 h following ingestion indicating that the residual effects of oral delta(9)-THC are minimal.

Conclusions: These data demonstrate that oral delta(9)-THC impairs episodic memory and learning in a dose-dependent manner whilst sparing perceptual priming and working memory.

Publication types

  • Clinical Trial
  • Comparative Study
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adolescent
  • Adult
  • Affect / drug effects*
  • Affect / physiology
  • Attention / drug effects
  • Attention / physiology
  • Cognition / drug effects*
  • Cognition / physiology
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Dronabinol / administration & dosage*
  • Dronabinol / blood
  • Humans
  • Male
  • Marijuana Smoking / psychology*
  • Mental Recall / drug effects
  • Mental Recall / physiology
  • Multivariate Analysis
  • Psychomotor Performance / drug effects*
  • Psychomotor Performance / physiology


  • Dronabinol