| Summary: | As legalization of cannabis continues to spread across the United States, many question the public health implications. The term “cannabis” is often used to refer to anything that comes from the plant and can be used recreationally (to get high or alter one’s current state) or medically (to treat a medical condition). While previous research has primarily focused on the impact of recreational cannabis use, few studies have examined cognitive outcomes associated with medical cannabis (MC) use and the potential for development of problematic use in MC patients. Given important distinctions among recreational users and MC patients, it is likely that these distinct populations of cannabis consumers will experience differential cognitive effects and potential for problematic cannabis use.
This dissertation is comprised of three studies. The first is a cross-sectional study that explores executive function and verbal learning and memory in recreational cannabis users relative to healthy controls who do not use cannabis, while also assessing whether cannabis use patterns (e.g., age of onset, urinary THC levels) influence findings. The second study is an observational, longitudinal study which examines executive function and memory, as well as changes in mood, anxiety, sleep, and quality of life in MC patients over 12 months of MC treatment relative to pre-MC treatment. In the third study, symptoms and behaviors associated with problematic cannabis use are examined in cohorts from study 1 and study 2. Specifically, scores on the Cannabis Use Disorder Identification Test – Revised (CUDIT-R) are assessed in MC patients over the course of treatment and also compared to a previously recruited cohort of recreational cannabis users; the validity of the CUDIT-R is also explored.
Despite previous research, in the current study recreational users did not exhibit cognitive decrements relative to healthy controls. In MC patents, cognitive performance was stable over the course of 12 months of MC treatment relative to pre-MC treatment performance, and overall they reported improved ratings of mood, anxiety, sleep, and some aspects of quality of life. Although the CUDIT-R suggests MC patients’ average scores do not meet the threshold for possible cannabis use disorder, analyses revealed this measure is not valid and therefore not appropriate in MC patients.
Although changes in cognition were not detected in recreational users or MC patients in the current studies, a number of methodological limitations (e.g., sample size and limited ability to adjust for confounding variables) must be considered as these factors likely affected study results. Future studies evaluating the impact of cannabis use will benefit from carefully considering the definition of cannabis itself, goal of use, product choice, and age of onset of use. Researchers and clinicians will also benefit from the development of screening tools specifically designed to assess cannabis use disorder in those who use cannabis for medical purposes.
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