People who use cannabis are often jokingly associated with having a bad memory. But is it true?
Episodic memory
(a type of long-term memory that involves conscious recollection of previous experiences together with their context in terms of time, place, associated emotions, etc.) is the most consistently reported cognitive impairment related to cannabis use(1).
This association is purported to be dose-dependent with greater memory deficits associated with higher levels of Δ-9-tetrahydrocannabinol (Δ-9-THC), the primary psychoactive ingredient in cannabis. Δ-9-THC disrupts memory processes through its impact on the brain’s endocannabinoid system which includes areas that underlie learning and memory functions such as
the hippocampus, amygdala, and prefrontal cortex(2).
Since the endocannabinoid system is also involved in circadian rhythm modulation and sleep, memory impairment due to long-term cannabis use may also in part be a downstream effect of Δ-9-THC’s impact on sleep, similar to what has previously been described in terms of depression(3).
Sleep disturbances such as shorter sleep duration, reduced rapid eye movement sleep, and slow wave sleep are often reported in people who use cannabis at a higher rate compared to those who don’t use cannabis(4).
Decrements in rapid eye movement and slow wave sleep are known to impair hippocampal-dependent learning and inhibit memory consolidation(5).
Findings on the effects of cannabis use on sleep are mixed, which may be related to moderators related to cannabis use (e.g., age of onset, timing effects – acute vs persistent effects)(6) or demographic characteristics such as sex (male vs female effects).
Although there is an understanding that cannabis impacts both sleep and memory independently, and the crucial role of sleep on learning and memory processes, there is a need to investigate how sleep may mediate these
outcomes from cannabis use.
A recent study investigated if poorer learning and memory performance in individuals with a cannabis use disorder relative to controls are mediated by sleep problems(5).
This was the first study to examine how sleep mediates the relationship between cannabis use and memory performance.
These initial findings indicate:
Given THC’s influence on CB1 receptors that leads to reductions in rapid eye movement and slow wave sleep, it is not surprising to find a mediating relationship on learning and memory outcomes.
The association of sleep and cannabis use disorder on memory performance was discovered primarily on spatial memory outcome, and not verbal memory outcomes. Persistent sleep problems may have a greater impact on right hemispheric functions such as spatial memory due to lower amounts of slow wave sleep that affect right hippocampal function related to spatial memory formation(7).
This differentiates with sleep deprivation, (i.e., ≥ 24 hours with no sleep), which affects left hemispheric functions such as verbal memory. No significant associations between sleep problems and memory performance were noted when testing differences in cannabis use behaviors among people with cannabis use disorder.
Past research indicates that
cannabis has differential effects over time related to tolerance. Specifically, sleep-promoting effects are more apparent among cannabis-naïve individuals during initial use whereas chronic cannabis use is thought to disrupt sleep due to dysregulation in
endocannabinoid system from prolonged exposure to THC(8).
The use of cannabis for sleep is one of the most common reasons for using cannabis in both clinical and non-clinical populations. Therefore, these initial findings indicate a role of sleep between cannabis use disorder and memory function are important to consider for the optimization of cannabis’ potential therapeutic effects on sleep, while mitigating potential harm.
These initial findings also imply that sleep may be an important entry point to improve cognitive function in those with cannabis use disorder. Additionally, these findings can also inform regulations around cannabis use, particularly concerning its availability as a sleep aid.
Now that you know how chronic cannabis use affects sleep and memory, what about CBD?
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References:
1. Blest-Hopley G, Giampietro V, Bhattacharyya S: A Systematic Review of Human Neuroimaging Evidence of Memory-Related Functional Alterations Associated with Cannabis Use Complemented with Preclinical and Human Evidence of Memory Performance Alterations. Brain Sci 10, 2020
2. Lorenzetti V, Lubman DI, Whittle S, et al: Structural MRI findings in long-term cannabis users: what do we know? Subst Use Misuse 45:1787-808, 2010
3. Maple KE, McDaniel KA, Shollenbarger SG, et al: Dose-dependent cannabis use, depressive symptoms, and FAAH genotype predict sleep quality in emerging adults: a pilot study. Am J Drug Alcohol Abuse 42:431-40, 2016
4. Winiger EA, Hitchcock LN, Bryan AD, et al: Cannabis use and sleep: Expectations, outcomes, and the role of age. Addict Behav 112:106642, 2021
5. Brown T, Ackerman RA, Kroon E, et al: The role of sleep in the link between cannabis use and memory function: evidence from a cross-sectional study. Am J Drug Alcohol Abuse 50:547-556, 2024
6. Choi S, Huang BC, Gamaldo CE: Therapeutic Uses of Cannabis on Sleep Disorders and Related Conditions. J Clin Neurophysiol 37:39-49, 2020
7. Whitehurst LN, Fogler K, Hall K, et al: The effects of chronic marijuana use on circadian entrainment. Chronobiol Int 32:561-7, 2015
8. Valentino RJ, Volkow ND: Drugs, sleep, and the addicted brain. Neuropsychopharmacology 45:3-5, 2020
