Cognitive Functioning Enhanced By Cannabis Use In Schizophrenia

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MedWire News: Cannabis use by patients with schizophrenia is associated with enhanced cognitive functioning, with both frequency and recency of use linked to better neuropsychological performance, conclude Australian researchers.

There is a lack of understanding of the neuropsychological effects of cannabis use in schizophrenia, partly due to conflicting evidence from the few studies that have explored the association.

To investigate further, Carissa Coulston, from the University of Sydney in New South Wales, and colleagues studied 60 males with schizophrenia/schizoaffective disorder and 17 healthy males, with the two groups matched for age, years of education, and premorbid intelligence quotient.

The researchers examined the participants' medical history, substance use, and psychiatric symptoms, and a neuropsychological battery was administered to determine attention/processing speed, executive functions, memory, and perceptual organization. They also analyzed urine samples to determine the patients' substance use within 24 hours of cognitive assessment.

The control group performed significantly better than the schizophrenia group on tests for psychomotor speed, inhibition speed, visual spatial rule adherence, cognitive flexibility, and immediate memory components.

Focusing on cannabis use in schizophrenia patients, the researchers discovered that 44 patients met the DSM-IV criteria for lifetime cannabis abuse/dependence. Of these, 11 were high frequency users over the previous year, seven were medium frequency users, and 34 were low frequency users.

In addition, 11 had cannabis abuse/dependence in the past week, seven had non-dependent cannabis use in the past week, seven had non-dependent cannabis use in the past month, but prior to the previous week, and nine had non-dependent cannabis use prior to the past month.

Logistic regression analysis revealed that more patients with lifetime cannabis abuse/dependence performed better on the psychomotor speed component than those without lifetime abuse/dependence. Frequency and recency of cannabis use were associated with better performance, particularly on the attention/processing speed and executive function domains.

While acknowledging the issues around cannabis use in schizophrenia patients, the team concludes in the journal Schizophrenia Research: "In essence, the findings of this study suggest that cannabinoids, via their agonistic effects on cannabinoid receptors in the forebrain, may have a potentially useful role in the treatment of high-order cognitive processes known to be impaired in schizophrenia."

Source: Schizophr Res 2007; 96: 169-184
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