Dissertation
Unique effects of chronic THC and CBD use in multiple sclerosis on cognitive and motor function, neuroimaging, and quality of life amid hazy cannabis legality
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2025
DOI: 10.25820/etd.008077
Abstract
Multiple Sclerosis (MS) patients often endure a wide range of debilitating symptoms—cognitive and motor impairments, pain, fatigue, sleep disturbances, and emotional challenges like anxiety and depression—that significantly reduce their quality of life. As existing treatments are frequently inadequate, many MS patients turn to alternative therapies, particularly cannabis and its two primary constituents, Δ-9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD). THC is primarily responsible for intoxicating effects, while CBD is known for its medicinal properties, leading patients to self-select consumption ratios based on symptom relief needs. Despite increasing use, there is limited research on how chronic THC and CBD use impacts functional outcomes, quality of life, and brain structure and function specifically in MS patients. This dissertation aims to fill this gap by examining these relationships in detail.
Chapter 2 investigates cognitive impairment, brain metabolism ([18F]-fluorodeoxyglucose positron emission tomography), grey matter volume (MRI), and quality of life indicators in THC-dominant, CBD-dominant, mixed-user, and non-user MS patients. While there were no differences in rates of cognitive impairment amongst any group, THCd users reported higher anxiety, and all cannabis groups exhibited unique changes in brain structure and metabolism, particularly in subcortical, frontal, and temporal regions. These findings challenge assumptions about cannabis-related cognitive decline and highlight the need for cannabinoid-specific analyses. Chapter 3 focuses on motor function and health-related quality of life (HRQoL), revealing no significant differences between cannabis users and non-users, suggesting chronic use may not accelerate motor decline, although sample size limits broader applicability. Chapter 4 addresses challenges in self-reported cannabis use, comparing subjective reports to blood plasma cannabinoid levels in 10 chronic users. Mismatches between reported and actual cannabinoid profiles in eight of ten participants underscore the unreliability of self-reporting, possibly due to recall bias or regulatory inconsistencies.
Lastly, Chapter 5 delves into the neurobiological underpinnings of anxiety in MS cannabis users, particularly in relation to the amygdala, a key anxiety-related brain region. Surprisingly, amygdala metabolism was not a significant predictor of anxiety, with only disease severity and cannabis group status showing predictive value. These results highlight the complex and multifactorial nature of anxiety in MS. Collectively, the dissertation challenges the generalizability of prior cannabis research focused on recreational users by providing MS-specific insights into the nuanced effects of chronic cannabis use. It further emphasizes that THC and CBD have distinct neuropsychological and physiological impacts, depending on their consumption ratios, suggesting a need for tailored therapeutic approaches. Additionally, the inconsistent regulatory environment complicates both patient access and research accuracy, impeding the development of evidence-based clinical guidelines. This work provides a critical foundation for clinicians seeking to understand the individualized potential of medical cannabis in MS care and calls for policy reforms that facilitate more rigorous scientific investigation.
Details
- Title: Subtitle
- Unique effects of chronic THC and CBD use in multiple sclerosis on cognitive and motor function, neuroimaging, and quality of life amid hazy cannabis legality
- Creators
- Justin R Deters
- Contributors
- Warren Darling (Advisor)Phillip Gander (Advisor)Laura L Boles PontoDavid Moser (Committee Member)Nathaniel Jenkins (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Health and Human Physiology
- Date degree season
- Summer 2025
- DOI
- 10.25820/etd.008077
- Publisher
- University of Iowa
- Number of pages
- xviii, 165 pages
- Copyright
- Copyright 2025 Justin R Deters
- Language
- English
- Date submitted
- 05/16/2025
- Description illustrations
- illustrations, tables, graphs, maps
- Description bibliographic
- Includes bibliographical references (pages 135-150).
- Public Abstract (ETD)
Multiple sclerosis (MS) is a complex neurological disease that can greatly impact a person s quality of life. Many individuals with MS turn to medical cannabis to help manage their symptoms, but research on its effects is still limited. This dissertation explores how different types of cannabis use products high in THC, CBD, or a mix of both affect anxiety, brain function, and overall well-being in people with MS.
The findings suggest that cannabis users should not be treated as a single group, as THC and CBD may have different effects. While cannabis use was not linked to differences in cognitive function, THC users showed higher anxiety levels than those using both THC and CBD. Additionally, differences in brain structure and activity were found in several regions, including the amygdala, which plays a role in emotion regulation. Importantly, product labeling was inconsistent, with some users testing positive for cannabis compounds they did not report using. This highlights a need for stricter regulation and quality control in medical cannabis products.
Despite the challenges of studying cannabis due to legal and regulatory barriers, these findings emphasize the importance of personalized cannabis treatment approaches for MS patients. Future research with verified product concentrations and larger sample sizes is needed to fully understand how cannabis may improve quality of life for those living with MS.
- Academic Unit
- Health, Sport, and Human Physiology
- Record Identifier
- 9984948239302771
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