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The role of cannabis in cognitive functioning of patients with schizophrenia.

Abstract

RATIONALE
Cognitive deficits are commonly found both in patients with schizophrenia (SCH) and in people with cannabis use disorders (CUD). Surprisingly, some small recent studies reported better cognitive performance in SCH patients with comorbid cannabis use disorders (SCH + CUD) compared to other SCH patients.
OBJECTIVES
The aim of the present study was to investigate the residual impact of CUD and specific patterns of consumption on cognition in a larger sample of SCH + CUD patients.
METHODS
We administered a cognitive test battery to 34 SCH and 35 currently abstinent SCH + CUD patients. We explored the association between patterns of cannabis consumption and cognitive performance. Potential confounds with influence on cognitive ability were assessed and controlled for.
RESULTS
SCH + CUD patients had poorer academic achievements and lower vocabulary scores, but they performed better in tests of verbal and working memory, visuomotor speed and executive function (p < .05). More frequent cannabis use was associated with better performance in attention and working memory tasks.
CONCLUSIONS
Although our findings might be interpreted as beneficial effect of cannabis use on cognition in patients with schizophrenia, we favorise an alternative interpretation: in our view, the better cognitive functioning of SCH + CUD patients may rather reflect a relatively lower vulnerability to psychosis compared to the SCH group. Lower vulnerability may correspond to a higher level of functioning such as cognitive ability. This conclusion is consistent with the view of cannabis playing a critical role in the manifestation of psychosis in at least some of the SCH + CUD patients.

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  • Publisher Full Text

    • Authors

    Schnell T, Koethe D, Daumann J, Gouzoulis-Mayfrank E

    Institution

    Department of Psychiatry and Psychotherapy, University Hospital of Cologne, Kerpener Str. 62, 50924, Cologne, Germany. thomas.schnell@uk-koeln.de

    Source

    Psychopharmacology 205:1 2009 Jul pg 45-52

    MeSH

    Adult
    Analysis of Variance
    Cannabis
    Chi-Square Distribution
    Cognition Disorders
    Female
    Humans
    Male
    Marijuana Abuse
    Neuropsychological Tests
    Schizophrenia
    Statistics, Nonparametric

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    19326102