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Compared to high and low cannabis use, moderate use is associated with fewer cognitive deficits in psychosis.

Ashley M. Schnakenberg Martin, K. Bonfils, Beshaun J. Davis, Elizabeth A. Smith, Kelly M. Schuder, Paul H Lysaker

Schizophrenia Research: Cognition December 1, 2016 DOI: 10.1016/j.scog.2016.09.001 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational study Peer reviewed
Sample size 66
Population Adults with schizophrenia
Topics Cannabis
Key findings Participants with moderate and heavy lifetime cannabis use showed less impairment in neurocognition and metacognition than those with low lifetime use, and moderate users showed less metacognitive impairment than both low and heavy users. The authors suggest a dose-related relationship between cannabis use and cognition may exist, though results could reflect pre-existing cognitive level influencing lifetime cannabis use or an interaction between use and cognitive function.

Abstract

Literature on the relationship of cannabis use and cognition in schizophrenia provides the paradoxical view that cannabis use is sometimes linked with less severe impairment in neurocognition. This paper explored the possibility that this is a reflection of a dose related response between lifetime cannabis use and two forms of cognition, neurocognition and metacognition, in schizophrenia. It was hypothesized that three groups of patients could be differentiated, those with (1) little to no cannabis use with poor levels of cognition, (2) moderate cannabis use and relatively better levels of cognition and (3) high cannabis use with relatively poorer levels of cognition. Sixty-six adults with schizophrenia completed assessments of neurocognition, metacognition and months of lifetime cannabis use. A k-means cluster analysis yielded three distinct groups based on these assessments. The clusters included: (1) low cannabis/poor cognition (n = 34); (2) heavy cannabis/moderately impaired cognition (n = 10); and (3) moderate cannabis/higher cognition (n = 22). Consistent with our hypothesis, participants with high and moderate lifetime cannabis use had lesser impairment of neurocognition and metacognition compared to low lifetime cannabis use. Participants with moderate lifetime cannabis use also had lesser impairment of metacognition compared to low and heavy use. These findings suggest that a dose related relationship exists between cannabis use and cognition. Results could be due to an influence of pre-existing cognitive level on likelihood of lifetime cannabis use, or to an interaction between use and cognitive function.

Comparable studies

Other observational and cohort studies on cannabis, most cited first.

Study Year Design Participants
High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population 2009 Case-control study n = 454
Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population 2013 Observational study
Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people 2000 Observational
Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline 2011 Observational cohort n = 1,923
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... 2005 Observational cohort n = 535

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Cannabis Addiction