Drug misuse boost to cognition refuted in schizophrenia
medwireNews: Analysis of the CATIE study participants has cast doubt on the purported link between illicit drug use and improved cognitive function in patients with schizophrenia.
The analysis by Amber Bahorik (University of Pittsburgh, Pennsylvania, USA) and colleagues involved 1009 CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) participants who had undergone radioimmunoassay testing of hair samples, so drug use was ascertained by objective testing rather than by self-report. Drug use was common, detected in 40% of the patients.
“Contrary to our hypotheses and the findings of prior research on neurocognition and drug use in schizophrenia, our results revealed patients who tested positive for drug use did not exhibit better cognitive function compared with those with negative results,” the researchers report in Schizophrenia Bulletin.
Scores on a battery of 11 neurocognitive tests were not significantly different between patients with any drug use and those with none. Nor did they differ, relative to nonusers, in patients who used multiple drugs, or any specific drug, including cannabis, which is the drug most frequently linked to improved cognition in schizophrenia patients.
Negative symptoms did not account for the lack of association between neurocognition and drug use, being associated with the former but not the latter. Further adjustment for demographic and clinical variables did not affect the results.
There was just one positive finding, with patients who used methamphetamine “quite unexpectedly” having significantly increased processing speed relative to nonusers, and this remained significant after correction for multiple inference testing. However, none of the other cognitive domains (verbal memory, vigilance, working memory, reasoning) differed in methamphetamine users.
Bahorik et al therefore conclude: “Taken together, our findings do not suggest a positive effect of drug use, cannabis or otherwise, on cognitive function for this sample.”
They believe that the previously reported positive association between drug use and neurocognition in schizophrenia patients “may be better explained by study-specific selection factors,” such as cannabis-induced psychosis and small sample sizes, “rather than actual increases in neurocognitive test performance in patients who use drugs.”
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By Eleanor McDermid, Senior medwireNews Reporter