title: Acute effects of THC on time perception in frequent and infrequent cannabis users.
abstract: BACKGROUND
  Cannabinoids have been shown to alter time perception, but existing literature has several limitations. Few studies have included both time estimation and production tasks, few control for subvocal counting, most had small sample sizes, some did not record subjects' cannabis use, many tested only one dose, and used either oral or inhaled administration of Δ⁹-tetrahydrocannabinol (THC), leading to variable pharmacokinetics, and some used whole-plant cannabis containing cannabinoids other than THC. Our study attempted to address these limitations.
  
  
  OBJECTIVE
  This study aims to characterize the acute effects of THC and frequent cannabis use on seconds-range time perception. THC was hypothesized to produce transient, dose-related time overestimation and underproduction. Frequent cannabis smokers were hypothesized to show blunted responses to these alterations.
  
  
  METHODS
  IV THC was administered at doses from 0.015 to 0.05 mg/kg to 44 subjects who participated in several double-blind, randomized, counterbalanced, crossover, placebo-controlled studies. Visual time estimation and production tasks in the seconds range were presented to subjects three times on each test day.
  
  
  RESULTS
  All doses induced time overestimation and underproduction. Chronic cannabis use had no effect on baseline time perception. While infrequent/nonsmokers showed temporal overestimation at medium and high doses and temporal underproduction at all doses, frequent cannabis users showed no differences. THC effects on time perception were not dose related.
  
  
  CONCLUSIONS
  A psychoactive dose of THC increases internal clock speed as indicated by time overestimation and underproduction. This effect is not dose related and is blunted in chronic cannabis smokers who did not otherwise have altered baseline time perception.
authors.affiliation: Department of Psychiatry, Yale School of Medicine, Yale University, New Haven, CT, USA. Richard.sewell@yale.edu
authors.forename: R Andrew
authors.initials: RA
authors.lastname: Sewell
authors.forename: Ashley
authors.initials: A
authors.lastname: Schnakenberg
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Elander
authors.forename: Rajiv
authors.initials: R
authors.lastname: Radhakrishnan
authors.forename: Ashley
authors.initials: A
authors.lastname: Williams
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Skosnik
authors.forename: Brian
authors.initials: B
authors.lastname: Pittman
authors.forename: Mohini
authors.initials: M
authors.lastname: Ranganathan
authors.forename: D Cyril
authors.initials: DC
authors.lastname: D'Souza
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000187:drug effects; D002188:Cannabis; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D013759:Dronabinol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000187:drug effects; D013998:Time Perception / Q000187:drug effects*; D055815:Young Adult
chemical_list: D013759:Dronabinol