Marijuana Does Not Affect the Brain? What Were These "Scientists" Smoking? May 11, 2006

In a preliminary study published today in the open access journal Harm Reduction Journal, researchers used diffusion tensor imaging to compare the brain tissue of young people who had used cannabis moderately as teenagers and young people who had not.

Lynn DeLisi and colleagues from the Nathan S. Kline Institute for Psychiatric Research and New York University School of Medicine used diffusion tensor imaging (DTI) to scan the brain of 10 young people who had smoked cannabis during adolescence. The participants were between 17 and 30 years old, they had smoked at least two to three times a week for one or more years during adolescence and had no personal or family history of mental health problems. They were matched for sex, age and social class of parents with 10 controls who had not smoked cannabis regularly as teenagers.

DTI is a magnetic resonance imaging (MRI) technique that enables a detailed look at the organisation of nerves in the brain and the measurement of brain volume.

DeLisi and her colleagues found no significant differences in brain integrity and brain volume between cannabis smokers and non-smokers. Although this preliminary study could be interpreted to suggest that moderate cannabis use has no direct adverse effects on brain structure and integrity, it is more likely that the methods used to analyze the brain in this study, were inadequate. Obviously, pot smoking effects the brain. The authors also warn that more research is necessary, both in a larger group of people and to see the effects of heavier use.