Mechanisms of treatment seeking and recovery in cannabis use disorder

Cannabis is the most commonly used illicit drug globally. The United Nations Office on Drugs and Crime (UNODC) estimates that approximately 3.8% of the population (188 million people) aged 15-64 used cannabis at least once in 2017. Although most people do not go on to use regularly, others develop a problematic pattern of use, characterised by continued use despite persistent adverse consequences. It is estimated that there are 22 million people worldwide with a cannabis use disorder (CUD) (Degenhardt et al. (2018)). European data suggests that treatment seeking for new cannabis use problems has increased by 76% in the past 10 years. Despite this increase, the majority of those with CUDs still do not seek help. Meanwhile current psychological therapies for CUD show only modest effects, and there are no accepted pharmacological treatments. This PhD project will investigate these problems in a series of studies by identifying who is vulnerable to cannabis use disorders, and which factors are predictive of treatment seeking. I will do this using data from the ALSPAC Bristol dataset which will provide detailed information on CUDs from onset and treatment seeking, to cessation and associated health and treatment outcomes. This will help to inform our understanding of the epidemiology of CUDs and to generate targeted, informed health information for increasing treatment seeking. As well as this, the PhD will address the shortcomings of current treatment options by providing detailed analysis and exploration of data suggesting a novel new treatment mechanism for CUD. I will explore this by examining prior evidence that suggests a non-intoxicating component of cannabis called cannabidiol (CBD), may be effective in reducing symptoms of CUD. My first study of the PhD will involve secondary data analysis of a previous clinical trial that found CBD was effective at reducing symptoms of CUD in frequent users who intended to quit. My analysis will focus on several cognitive tasks from the study protocol, including salience attribution, response inhibition and executive function. I will investigate which task performance(s) may mediate the effectiveness of CBD on reducing symptoms of CUD. The aim will be to identify the cognitive mechanisms by which CBD shows treatment efficacy. I will later run an experimental medicine study looking at the effects of a single dose of CBD on reducing symptoms of CUD. I will investigate the proposed mechanisms identified from study 1, which will hopefully provide a novel experimental platform to analyse new treatments for CUD. This study will involve using EEG and eye-tracking to thoroughly probe the neural and physiological underpinnings of these effects.