Citation

Bogaty SER, Lee RSC, Hickie IB, Hermens DF. J. Psychiatr. Res. 2018; 99: 22-32.

Affiliation

Brain and Mind Centre, University of Sydney, Sydney, NSW, Australia; Sunshine Coast Mind and Neuroscience Thompson Institute, University of the Sunshine Coast, Birtinya, QLD, Australia. Electronic address: dhermens@usc.edu.au.

Copyright

(Copyright © 2018, Elsevier Publishing)

DOI

10.1016/j.jpsychires.2018.01.010

PMID

29407284

Abstract

OBJECTIVE: Adult psychosis patients (i.e. over the age of 25 years) who are also lifetime cannabis users (CANN±) appear to exhibit superior cognition compared to never-using patients (CANN-). The objective of this meta-analysis was to evaluate the cognitive differences between CANN- and patients who currently use cannabis (CANN+) (i.e. during the CANN± patients' cannabis-using stage). Specifically, focusing on young patients under the age of 25 years, the typical stage of both psychosis- and cannabis-onset.

METHOD: Of the 308 studies identified through database searches and secondary referencing, 14 compared neurocognition of CANN+ and CANN- in young people with psychotic disorders (mean age between 15 and 45 years). Effect sizes were extracted using neurocognitive test performance between CANN+ and CANN- and random effects modelling was conducted on pooled ES and moderator analyses.

RESULTS: CANN+ performed worse on several cognitive domains (i.e. premorbid IQ, current IQ, verbal learning, verbal working memory, motor inhibition) compared to CANN-. The association between age and performance in CANN+ cognition was varied, with older age predictive of worse performance in processing speed, sustained attention, verbal memory, and better performance in verbal learning and very fluency. Of note, CANN+ outperformed CANN- in tests of conceptual set-shifting.

CONCLUSION: These results are consistent with previous findings indicating that CANN+ demonstrate poorer neurocognition than CANN-; and that this is exacerbated with increasing age. Our findings demonstrate significant cognitive differences between patients with CANN+ versus CANN- even at early-onset psychosis, which could suggest a different underlying mechanism towards psychosis for cannabis users.

Copyright © 2018 Elsevier Ltd. All rights reserved.

Language: en

Keywords

Cognition; Comorbidity; Early-onset psychosis; Marijuana; Schizophrenia; Young people