Results from a US study suggest that bipolar I disorder (BD I) patients with a history of cannabis use have better neurocognitive function than those who have not used cannabis.
The team found that BD I patients with cannabis use disorder (CUD) performed better on measures of attention, processing speed, and working memory than other BD I patients, despite being more likely to have a history of psychosis, indicating a more severe disease course.
"These data could be interpreted to suggest that cannabis use may have a beneficial effect on cognitive functioning in patients with severe psychiatric disorders," comment Raphael Braga (The Zucker Hillside Hospital, Glen Oaks, New York) and team.
"However, it is also possible that these findings may be due to the requirement for a certain level of cognitive function and related social skills in the acquisition of illicit drugs."
The results come from a study of 200 BD I patients, of whom 50 had CUD.
All of the participants underwent clinical assessments and completed a neurocognitive test battery.
There were no significant differences between patients with and without CUD regarding age, racial background, or highest education level achieved, the researchers note in Psychiatry Research.
However, patients with CUD were more likely to have a history of psychosis than those without, at 82.0% versus 67.3%.
Nevertheless, patients with CUD had significantly better attention, processing speed/set-shifting, and working memory than those without, as indicated by scores on the Digits forward test (7.00 vs 6.25), the Trails B test (93.32 vs 120.77 seconds), and the Digits Backward test (4.93 vs 4.23), respectively.
Braga and team conclude: "These analyses indicate an interesting pattern suggesting superior neurocognitive performance among bipolar patients with comorbid CUD when compared to bipolar patients without a history of cannabis use.
"Moreover, this cognitive advantage is noted in spite of evidence of a more severe clinical course."
They add: "We hope that the results from our study will help guide and encourage future large studies and help further elucidate the multifaceted associations and possible impact of cannabis use in bipolar disorder."
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