Marijuana alters the human cerebellar clock

Neuroreport. 2003 Jun 11;14(8):1145-51. doi: 10.1097/00001756-200306110-00009.


The effects of marijuana on brain perfusion and internal timing were assessed using [15O] water PET in occasional and chronic users. Twelve volunteers who smoked marijuana recreationally about once weekly, and 12 volunteers who smoked daily for a number of years performed a self-paced counting task during PET imaging, before and after smoking marijuana and placebo cigarettes. Smoking marijuana increased rCBF in the ventral forebrain and cerebellar cortex in both groups, but resulted in significantly less frontal lobe activation in chronic users. Counting rate increased after smoking marijuana in both groups, as did a behavioral measure of self-paced tapping, and both increases correlated with rCBF in the cerebellum. Smoking marijuana appears to accelerate a cerebellar clock altering self-paced behaviors.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Brain / diagnostic imaging
  • Brain / drug effects*
  • Brain / physiology
  • Cannabis / chemistry
  • Cannabis / toxicity*
  • Case-Control Studies
  • Cerebellum / drug effects*
  • Cerebellum / physiology
  • Cerebrovascular Circulation / drug effects
  • Cognition
  • Dronabinol / blood
  • Ego
  • Female
  • Heart Rate
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Male
  • Marijuana Smoking / adverse effects
  • Marijuana Smoking / blood
  • Marijuana Smoking / physiopathology*
  • Neuropsychological Tests
  • Placebos
  • Psychomotor Performance
  • Regional Blood Flow / physiology
  • Tomography, Emission-Computed / methods
  • Verbal Behavior


  • Placebos
  • Dronabinol