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Open Access 01-12-2022 | Multiple Sclerosis | Research

The effect of medical cannabis on cognitive functions: a systematic review

Authors: Anders Wieghorst, Kirsten Kaya Roessler, Oliver Hendricks, Tonny Elmose Andersen

Published in: Systematic Reviews | Issue 1/2022

Abstract

Background

Cannabis-based medicines are widely used in the treatment of a number of medical conditions. Unfortunately, cognitive disturbances are often reported as adverse events, although conversely, cognitive improvements have been reported. Hence, the objective of the present study was to identify, critically appraise and synthesise research findings on the potential impact of cannabis-based medicines on cognitive functioning.

Methods

Four databases (EMBASE, PsycINFO, PubMed and Scopus) were systematically searched. Studies were included if they provided findings on the impact of cannabis-based medicines in controlled settings on cognitive functioning measured by recognised cognitive tests in human adults. Study participants were required to be their own case-control, and neither studies on abuse, abstinences, patients with severe neurodegenerative diseases nor cancer-related pain conditions were included. Screening, risk of bias assessment and data extraction were conducted independently by two researchers. Findings were tabulated and synthesised by outcome.

Findings

Twenty-three studies were included, comprising a total of N = 917. Eight studies used Sativex as the cannabis-based medicine two used Epidiolex, two other studies used sprays, three studies used gelatine capsules, five smoked cannabis, two other and finally one studied cannabis withdrawal. Fifteen studies reported non-significant findings; six reported cognitive impairments; one study found cognitive improvement and a single study found improvement following withdrawal. Thirteen studies had cognitive or neuropsychological functioning as the primary outcome.

Conclusions

Due to a large heterogeneity and methodological limitations across studies, it is not possible to make any definite conclusions about the impact of cannabis-based medicines on cognitive functioning. However, the majority of high-quality evidence points in the direction that the negative impact of cannabis-based medicines on cognitive functioning is minor, provided that the doses of THC are low to moderate. On the other hand, long-term use of cannabis based medicines may still adversely affect cognitive functioning. In the studies that found impaired cognitive functioning to be significant, all of the test scores were either within the normal range or below what would be characterised as a neuropsychologically cognitive impairment.

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Title: The effect of medical cannabis on cognitive functions: a systematic review
Authors: Anders Wieghorst
Kirsten Kaya Roessler
Oliver Hendricks
Tonny Elmose Andersen
Publication date: 01-12-2022
Publisher: BioMed Central
Keyword: Multiple Sclerosis
Published in: Systematic Reviews / Issue 1/2022
Electronic ISSN: 2046-4053
DOI: https://doi.org/10.1186/s13643-022-02073-5

Keynote webinar | Spotlight on medication adherence

Springer Medicine

The effect of medical cannabis on cognitive functions: a systematic review

Abstract

Background

Methods

Findings

Conclusions

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Abstract

Background

Methods

Findings

Conclusions

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