Brain morphological changes and early marijuana use: a magnetic resonance and positron emission tomography study

J Addict Dis. 2000;19(1):1-22. doi: 10.1300/J069v19n01_01.


Background: The focus of this report is on the possible role that the age of first use of marijuana may play on brain morphology and function.

Methods: Magnetic resonance imaging (MRI) and positron emission tomography (PET) were utilized to study 57 subjects. Brain volume measures (whole brain, gray matter, white matter and lateral ventricle volumes), global cerebral blood flow (CBF) and body size were evaluated.

Results: There are three primary findings related to age of first use of marijuana. Subjects who started using marijuana before age 17, compared to those who started later, had smaller whole brain and percent cortical gray matter and larger percent white matter volumes. Functionally, males who started using marijuana before 17 had significantly higher CBF than other males. Both males and females who started younger were physically smaller in height and weight, with the effects being greater in males.

Conclusions: These findings suggest that the age at which exposure to marijuana begins is important. Early adolescence may be a critical period for effects that are not present when exposure begins later. These results are discussed in light of reported effects of marijuana on gonadal and pituitary hormones.

Publication types

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

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Body Constitution
  • Brain / blood supply
  • Brain / drug effects*
  • Brain / pathology
  • Cannabinoids / adverse effects*
  • Cephalometry
  • Cerebral Cortex / blood supply
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / pathology
  • Cerebral Ventricles / blood supply
  • Cerebral Ventricles / drug effects
  • Cerebral Ventricles / pathology
  • Female
  • Humans
  • Magnetic Resonance Imaging*
  • Male
  • Marijuana Abuse / diagnosis*
  • Marijuana Abuse / physiopathology
  • Regional Blood Flow / drug effects
  • Tomography, Emission-Computed*


  • Cannabinoids