title: Neurophysiological functioning of occasional and heavy cannabis users during THC intoxication.
abstract: BACKGROUND
  Experienced cannabis users demonstrate tolerance to some of the impairing acute effects of cannabis.
  
  
  OBJECTIVE
  The present study investigates whether event-related potentials (ERPs) differ between occasional and heavy cannabis users after acute Δ9-tetrahydrocannabinol (THC) administration, as a result of tolerance.
  
  
  METHODS
  Twelve occasional and 12 heavy cannabis users participated in a double-blind, placebo-controlled, crossover study. On two separate days, they smoked a joint containing 0 or 500 μg/kg body weight THC. ERPs were measured while subjects performed a divided attention task (DAT) and stop signal task (SST).
  
  
  RESULTS
  In the DAT, THC significantly decreased P100 amplitude in occasional but not in heavy cannabis users. P300 amplitude in the DAT was significantly decreased by THC in both groups. The N200 peak in the SST was not affected by treatment in neither of the groups. Performance in the SST was impaired in both groups after THC treatment, whereas performance in the DAT was impaired by THC only in the occasional users group.
  
  
  CONCLUSIONS
  The present study confirms that heavy cannabis users develop tolerance to some of the impairing behavioral effects of cannabis. This tolerance was also evident in the underlying ERPs, suggesting that tolerance demonstrated on performance level is not (completely) due to behavioral compensation.
authors: Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University, P.O. Box 616, 6200MD Maastricht, The Netherlands. e.theunissen@maastrichtuniversity.nl
authors: Eef L
authors: EL
authors: Theunissen
authors: Gerold F
authors: GF
authors: Kauert
authors: Stefan W
authors: SW
authors: Toennes
authors: Manfred R
authors: MR
authors: Moeller
authors: Anke
authors: A
authors: Sambeth
authors: Mathieu M
authors: MM
authors: Blanchard
authors: Johannes G
authors: JG
authors: Ramaekers
mesh_terms: D000328:Adult; D001288:Attention / Q000187:drug effects / Q000502:physiology; D058256:Brain Waves / Q000187:drug effects* / Q000502:physiology*; D004311:Double-Blind Method; D013759:Dronabinol / Q000493:pharmacokinetics / Q000494:pharmacology*; D004361:Drug Tolerance / Q000502:physiology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D002189:Marijuana Abuse / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000187:drug effects* / Q000502:physiology*
chemical_list: D013759:Dronabinol