MedWire News: Schizophrenia patients with a history of cannabis use disorder show better function on a range of cognitive tests compared with their peers with no such history, study results show.
The authors of the study do not, however, believe that cannabis improves cognition per se, but rather suggest that the CUD group has inherently better social skills, making them more likely to encounter the drug.
“Despite the controversy related to the causal relationship between CUD and schizophrenia, several lines of research suggest that patients with comorbid CUD may represent a clinically distinct subgroup of schizophrenia,” say Pamela DeRosse (The Zucker Hillside Hospital, Glen Oaks, New York, USA) and colleagues in the journal Schizophrenia Research.
To investigate further the researchers retrospectively assessed 455 schizophrenia patients, of whom 175 had a history of CUD (CUD+) and 280 had no such history (CUD–).
Participants were administered a battery of cognitive tests measuring verbal skill (California Verbal Learning Test [CVLT]-Abridged; Controlled Oral Word Association Test [COWAT], Animal Naming) and processing speed (Wechsler Adult Intelligence Test-Revised [WAIS-R]-Digit Span; Trail Making Tests A and B).
They also adjusted for key demographic variables including gender, race, age, age at onset of illness, parental socioeconomic status, premorbid IQ, and education level.
Patients in the CUD+ group demonstrated significantly better performance on measures of processing speed, verbal fluency, and verbal learning and memory compared with patients in the CUD- group.
In addition the CUD+ group had better global function scores than the CUD- group, which the researchers say demonstrates that comorbid CUD may represent a subgroup of schizophrenia with better social interaction ability.
One of the shortcomings of the study was the lack of uniformity in duration of time since last use of cannabis. However the researchers say this shouldn’t have skewed the results since the effects of cannabis on cognitive function are relatively short-lived.
“Additional data are needed, however, to elucidate how and why the social environment of patients with schizophrenia may increase the odds of coming in contact with cannabis,” DeRosse and colleagues conclude.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
Free abstract
