Reductions in white brain matter have been linked to cognitive impairments. Decreased white matter is one symptom of schizophrenia and has also been found in people who are at risk for psychosis. This same symptom has also been discovered in individuals with long-term cannabis use. However, little research has examined whether or not extensive cannabis use increases the risk for psychotic symptoms, or if schizophrenic individuals who use cannabis experience poorer cognitive functioning than those who do not use cannabis. In an attempt to address this gap, N. Solowij of the School of Psychology at the University of Wollongong in Australia conducted a study looking at how white brain matter varied in different classifications of individuals. Solowij recruited 15 cannabis users without schizophrenia, 8 with schizophrenia, 9 individuals with schizophrenia alone, and 16 healthy, nonusing individuals.
Solowij analyzed the participants using magnetic resonance imaging scans (MRIs) and discovered that the healthy individuals who used cannabis had a 23.9% reduction in white brain matter compared to those who did not. Additionally, cannabis users who also had schizophrenia had 29.7% less white brain matter than those who did not use. Because decreased white brain matter is linked to impaired cognitive functioning and reasoning, the results suggest that individuals who use cannabis could become vulnerable to psychotic-type symptoms. Further, for individuals with schizophrenia, using cannabis could increase symptom severity and duration. Overall, the findings of the study imply that people with long-term cannabis use have significantly less white brain matter than individuals with schizophrenia who do not use cannabis. Solowij also pointed out that individuals with schizophrenia, specifically those who develop it in early adulthood, may actually change the course of their brain maturation by using cannabis. Clinicians treating individuals with schizophrenia should consider exploring their clients’ cannabis use in order to better understand and manage the severity of their symptoms in relation to their illness.
Solowij, N., Yucel, M., Respondek, C., Whittle, S., Lindsay, E., Pantelis, C., Lubman, D. I. Cerebellar White-Matter Changes in Cannabis Users With and Without Schizophrenia. Psychological Medicine 41.11 (2011): 2349-359. Print.
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