Is cannabis use associated with an increased risk of dementia?

From the Guidelines

Cannabis use is not definitively associated with an increased risk of dementia, but heavy, long-term use, especially when initiated in adolescence, may potentially affect brain structure and function in ways that could influence dementia risk. The current evidence on the relationship between cannabis use and dementia risk is mixed and inconclusive, with some studies suggesting potential risks and others indicating possible benefits from certain cannabinoids 1. Some key points to consider include:

• The effects of THC on the brain, particularly in regions related to memory, such as the hippocampus, where changes in structure have been observed among adults who initiated heavy cannabis use in adolescence 1.
• The potential for neuroprotective properties of certain cannabinoids like CBD, which could benefit brain health.
• The influence of factors such as age of first use, frequency, duration, potency of cannabis used, and genetic predisposition on the risk.
• The greater vulnerability of the developing brain to cannabis use, suggesting that adolescent-onset use may pose greater risks.
• The potential vascular risks associated with smoking cannabis, similar to those of tobacco, which could contribute to vascular dementia. Given the complexity and uncertainty of the current evidence, it is crucial to approach cannabis use with caution, especially for adolescents and young adults, and to prioritize further research into the long-term effects of cannabis on brain health and dementia risk.

From the Research

Cannabis Use and Dementia Risk

• The current evidence on the association between cannabis use and dementia risk is limited and inconclusive 2, 3, 4, 5, 6.
• Some studies suggest that cannabinoids, such as THC and CBD, may have neuroprotective effects and potentially reduce the risk of dementia 3, 6.
• However, other studies have found no significant association between cannabis use and dementia risk, and some have raised concerns about the potential negative effects of cannabis on cognitive function, particularly in older adults 2, 4.

Key Findings

• A 2021 systematic review found that cannabinoids may have little or no clinically important effect on cognition or behavioral and psychological symptoms of dementia, but the evidence was of low or very low certainty 2.
• A 2024 overview of prospective clinical studies and randomized clinical trials suggested that THC and CBD may have a positive impact on behavioral and psychological symptoms of dementia, but more research is needed to establish clinical efficiency and optimal dosing 3.
• A 2019 review highlighted the potential effects of cannabis on brain structure, function, and cognition, and suggested that age limits and guidelines for use should be considered 4.
• A 2023 clinical trial protocol aimed to investigate the effects of CBD on neurobiological, behavioral, and psychological symptoms in early-stage dementia, but the results are not yet available 5.
• A 2020 review found that cannabinoids, particularly CBD, may be effective and safe for use in older people with agitation associated with dementia, but further research is needed to confirm these findings 6.

Research Gaps

• More research is needed to fully understand the relationship between cannabis use and dementia risk, including the potential benefits and harms of cannabinoids for people with dementia 2, 3, 4, 5, 6.
• Further studies should investigate the effects of different types and doses of cannabinoids, as well as the potential interactions with other medications and health conditions 3, 5, 6.