Although cannabis is the most widely used illicit drug in the world, the long-term effect of its use in the brain remains controversial. In order to determine whether adolescence and early-adulthood cannabis use is associated with gross volumetric and gyrification abnormalities in the brain, we set up a cross-sectional study using structural magnetic resonance imaging in a sample of general population subjects. Thirty cannabis-using subjects (mean age, 25.7 years; mean duration of regular use, 8.4 years, range: 3-21) with no history of polydrug use or neurologic/mental disorder and 53 non-using control subjects (mean age, 28.6 years) were included. Cannabis users had a 1.7% reduction in gray matter volume and a 31.3% increase in cortical cerebrospinal fluid (CCSF) volume in the right hemisphere; bilaterally decreased concavity of the sulci in the frontal, temporal and parietal lobes; and thinner sulci in the right frontal and parietal lobes. CCSF volume was significantly correlated with less concave sulci and more convex gyri. Among non-users, age was significantly correlated with decreased gyrification (i.e., less concave sulci and more convexe gyri) and decreased cortical thickness, supporting the notion of age-related gyrification changes. However, among cannabis users gyrification indices did not show significant dependency on age, age of regular cannabis use initiation, or cumulative exposure to cannabis. These results suggest that cannabis use in adolescence and early-adulthood might involve a premature alteration in cortical gyrification similar to what is normally observed at a later age, probably through disruption of normal neurodevelopment. However, further prospective longitudinal research is needed to examine the mechanisms of this long-term cannabis related harm and the possible recovery after abstinence.

Trabajo presentado al 39th annual meeting of Neuroscience celebrado en Chicago del 17 al 21 de octubre de 2009.

Plan Nacional de drogas 2005- SCO/3246/2004 and Instituto de Salud Carlos III FIS PI050427.

Peer Reviewed