Therapeutic Effects of Prolonged Cannabidiol Treatment on Psychological Symptoms and Cognitive Function in Regular Cannabis Users: A Pragmatic Open-Label Clinical Trial.

Nadia Solowij,Lisa-Marie Greenwood,Samantha J Broyd,Julie-Anne Prick,Jennifer H Martin,Shanlin Fu,Nagesh Pai,Murat Yücel,Camilla Beale,Chao Suo,Rodney J Croft,Peter Galettis,Hendrika Van Hell

doi:10.1089/can.2017.0043

Abstract

Introduction: Chronic cannabis use has been associated with impaired cognition and elevated psychological symptoms, particularly psychotic-like experiences. While Δ9-tetrahydrocannabinol (THC) is thought to be primarily responsible for these deleterious effects, cannabidiol (CBD) is purported to have antipsychotic properties and to ameliorate cognitive, symptomatic, and brain harms in cannabis users. However, this has never been tested in a prolonged administration trial in otherwise healthy cannabis users. Here, we report the first study of prolonged CBD administration to a community sample of regular cannabis users in a pragmatic trial investigating potential restorative effects of CBD on psychological symptoms and cognition.Materials and Methods: Twenty frequent cannabis users (16 male, median age 25 years) underwent a 10-week open-label trial of 200 mg of daily oral CBD treatment, while continuing to use cannabis as usual. The majority of participants were daily cannabis users who had used cannabis for several years (median 5.5 years of regular use). Participants underwent psychological and cognitive assessments at baseline (BL) and post-treatment (PT) and were monitored weekly throughout the trial.Results: CBD was well tolerated with no reported side effects; however, participants retrospectively reported reduced euphoria when smoking cannabis. No impairments to cognition were found, nor were there deleterious effects on psychological function. Importantly, participants reported significantly fewer depressive and psychotic-like symptoms at PT relative to BL, and exhibited improvements in attentional switching, verbal learning, and memory. Increased plasma CBD concentrations were associated with improvements in attentional control and beneficial changes in psychological symptoms. Greater benefits were observed in dependent than in nondependent cannabis users.Conclusions: Prolonged CBD treatment appears to have promising therapeutic effects for improving psychological symptoms and cognition in regular cannabis users. Our findings require replication given the lack of a placebo control in this pragmatic trial, but suggest that CBD may be a useful adjunct treatment for cannabis dependence.

Highlights

Chronic cannabis use has been associated with impaired cognition and elevated psychological symptoms, psychotic-like experiences
On the basis of reviewed literature, we focused on symptoms of depression, trait anxiety, and psychosis-proneness,[4,25,26] and cognitive performance within the domains of attention/executive function and learning and memory, being the most sensitive to the deleterious effects of chronic cannabis use.[5]
Since this was a naturalistic study of cannabis users in the community, and the participant was not an outlier on any measure, his data were retained in the analyses reported in this study

Summary

Introduction

Chronic cannabis use has been associated with impaired cognition and elevated psychological symptoms, psychotic-like experiences. While D9-tetrahydrocannabinol (THC) is thought to be primarily responsible for these deleterious effects, cannabidiol (CBD) is purported to have antipsychotic properties and to ameliorate cognitive, symptomatic, and brain harms in cannabis users This has never been tested in a prolonged administration trial in otherwise healthy cannabis users. Despite promising evidence of the therapeutic effects of CBD, no study to date has examined the potentially restorative effects of prolonged CBD administration to cannabis users

Methods

Results

Conclusion