Using a sophisticated brain imaging technique called diffusion tensor imaging (DTI), researchers analyzed the brains of groups of adolescents: healthy, non-drug users; heavy marijuana smokers (daily use for at least one year); and schizophrenic patients.
The investigators believe chronic exposure to marijuana was responsible for certain abnormalities in the development of neural fibers, which are associated with the brain's higher levels of language and auditory functions.
Dr. Ashtari, associate professor at New York's Albert Einstein College of Medicine says, "Because this language/auditory pathway continues to develop during adolescence, it is most susceptible to the neurotoxins introduced into the body through marijuana use."
The findings of this study go along with several other lines of evidence that suggest a contribution of cannabis and/or abnormalities in the brain can lead to a higher prevalence of schizophrenia.
Another study, conducted by Cyril D'Souza from the Yale School of Medicine, had researchers administer THC, the main active ingredient in cannabis, to subjects who were screened for any vulnerability to schizophrenia. Some subjects developed symptoms resembling those of schizophrenia that lasted approximately thirty minutes to one hour.
These symptoms included suspiciousness, unusual thoughts, paranoia, thought disorder, blunted affect, reduced spontaneity, reduced interaction with the interviewer, and problems with memory and attention.
According to the National Institute on Drug Abuse, approximately 3.1 million Americans, age 12 and older, use marijuana on a daily or almost daily basis. In 2004, 5.6 percent of 12th graders reported daily use of marijuana.
