Long-term effects of cannabis on eye movement control in reading

Psychopharmacology (Berl). 2010 Mar;209(1):77-84. doi: 10.1007/s00213-009-1769-z. Epub 2010 Jan 21.

Abstract

Introduction: Cannabis is known to produce substantial acute effects on human cognition and visuomotor skills. Many recent studies additionally revealed rather long-lasting effects on basic oculomotor control, especially after chronic use. However, it is still unknown to what extent these deficits play a role in everyday tasks that strongly rely on an efficient saccade system, such as reading.

Materials and methods: In the present study, eye movements during sentence reading of 20 healthy long-term cannabis users (without acute tetrahydrocannabinol-intoxication) and 20 control participants were compared. Analyses focused on both spatial and temporal parameters of oculomotor control during reading.

Results: Long-term cannabis users exhibited increased fixation durations, more revisiting of previously inspected text, and a substantial prolongation of word viewing times, which were highly inflated for longer and less frequent words.

Discussion: The results indicate that relatively subtle performance deficits on the level of basic oculomotor control scale up as task complexity and cognitive demands increase.

MeSH terms

  • Adult
  • Cognition / drug effects
  • Eye Movements / drug effects*
  • Female
  • Fixation, Ocular / drug effects*
  • Humans
  • Male
  • Marijuana Abuse / complications*
  • Middle Aged
  • Oculomotor Muscles / drug effects
  • Reading
  • Time Factors
  • Young Adult