What it is:
Cannabis is one of the most widely used plants around the world. It has a rapid growth rate of three to four months to maturity and is consumed recreationally and medicinally. Similar to bamboo, it is also formulated into a range of industrial products, including textiles, cosmetics, bioplastics, paper, and more.
Cannabis is thought to have first been domesticated in southeast Asia nearly 12,000 years ago, having diversified and spread worldwide in the years since. In the United States, cannabis is now fully legal for recreational use in 23 states, plus the District of Columbia. With this move towards legalization in many places over recent years, the consumer market has grown exponentially. Many people are now using cannabis products for relaxation and sleep, which has garnered interest from sleep researchers for its potential as a therapeutic.
The purported claims:
Cannabis acts on the body’s endocannabinoid system.
While it contains many different chemical compounds, the dominant and best-known of the cannabinoids are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).
Occasional light use may improve sleep.
Heavy daily use negatively impacts sleep.
What the science says:
Cannabis Overview
Cannabis is a complex plant and contains more than 400 chemical compounds, 60 of which are cannabinoids. The main compounds include psychoactive delta-9-tetrahydrocannabinol (THC), which is responsible for the “high” during use, and cannabidiol (CBD), which is non-psychotropic and marketed primarily for its sedating properties.
Two species are consumed medicinally and recreationally: Cannabis sativa and Cannabis indica. The former is typically thought of as having proportionally higher THC than CBD, resulting in a more uplifting or activating high, while C. indica is generally consumed by those desiring proportionally greater CBD in favor of sedating or calming effects. Interestingly, scientific research has been unable to determine whether there exists a significant difference between THC and CBD content among the two species, and there are likely many factors that ultimately determine the THC:CBD ratio of the final product.
Cannabis acts on the endocannabinoid system within the central and peripheral nervous system. This system controls many important physiological processes, including pain, temperature regulation, inflammation, emotion, learning, memory, and sleep. We produce specific molecules within the body (endogenous cannabinoids) that bind to and activate the receptors in this system. The cannabinoids in cannabis also modulate this system.
Sleep
Approximately 30% of American adults experience some type of sleep complaint, with 10% meeting the criteria for insomnia disorder diagnosis. It’s unclear how many people use cannabis to treat their sleep problems, but research has been underway for several decades to determine how THC and CBD modulate sleep quality.
A recent meta-analysis combined data from 31 different studies and found that, interestingly, THC showed more promise than CBD at offering a potential benefit to sleep. This was surprising given that CBD is the sedating cannabinoid and is non-psychoactive.
Cannabis appears to be most promising for helping sleep among those who experience sleep loss due to pain. Pain management is one of the main reasons for medical prescriptions, as well as treating nausea and vomiting during chemotherapy.
Where cannabis has been tested specifically for sleep in the absence of pain, improvements are typically subjective, or self-reported, rather than anything noticeable on the electroencephalogram (EEG) itself. Sleep rarely appears to be any deeper (i.e. consisting of more slow wave activity) after cannabis use, though users may report that they felt they slept more deeply. This highlights the importance of perceived sleep quality. In general, if a person feels they got enough sleep and feel refreshed and alert the next day, they probably did.
Occasional cannabis use typically makes people fall asleep more quickly. It can also decrease the amount of time spent in rapid eye movement (REM) sleep. In one study, 40, 60, and 180mg of CBD resulted in less dream recall, likely reflecting less REM sleep. THC doses of 10, 20, and 30mg resulted in a shorter sleep latency, or time to fall asleep.
Cannabinoids primarily bind to two types of receptors within the endocannabinoid system: CB1 and CB2. These receptors trigger a whole cascade of processes within the cell, including the ability to alter subsequent gene expression. CB1 receptors are mainly found in the brain, whereas CB2 receptors are mainly found throughout the rest of the body (including on immune cells,) with proportionally much lower presence in the brain. THC and CBD bind to both of these receptors, but THC does so with a higher affinity. In other words, it will bind preferentially over CBD.
Blocking the CB1 receptor increases time spent awake, and decreases both slow-wave and REM sleep duration. When these receptors are activated, however, this increases time spent asleep. It has been shown that the number of CB1 receptors decreases with age. Fewer receptors means fewer binding sites for cannabinoids (whether endogenous ones we produce ourselves, or through cannabis use) to promote sleep. This may be one of the mechanisms by which sleep difficulties can appear in later life. Interestingly, however, one study showed that rats increase the number of CB1 receptors on their cells following sleep deprivation. Whether humans can do something similar is unclear.
The endocannabinoid system experiences its own circadian rhythm. One of the natural activators of this system, 2-arachidonylglycerol (2-AG), exhibits 24h variation, with the lowest levels mid-sleep. Circulating 2-AG increases upon wake and peaks in the afternoon among normal, healthy humans. Another compound, anandamide, is highest upon wake and lowest at bedtime, similar to the natural rhythm of cortisol. Interestingly, though, administration of exogenous (meaning: comes from outside the body) anandamide increases slow wave and REM sleep and reduces wakefulness in rats, despite endogenous anandamide levels being low in humans at bedtime. This suggests that these compounds serve multiple important roles in the body, other than regulating sleep alone.
Cannabis and sleep disorders
When it comes to insomnia, heavy cannabis use is not recommended. Heavy users tend to experience REM sleep suppression, and this is problematic given that REM sleep is associated with emotion processing and certain types of memory formation. If daily cannabis use stops, this can trigger withdrawal, during which the sleeper will experience a rebound in insomnia symptoms or REM sleep. When the latter occurs, proportionally more time than usual is spent in REM sleep, which can trigger intense dreams and sleep disturbances. This is also typically accompanied by less deep sleep. This combination can disrupt mood and daytime function.
In a CBD-only study, healthy people had no withdrawal after consuming 750mg for four weeks. It appears that the combination of CBD and THC is what can lead to withdrawal in the long-term. CBD is anxiolytic, meaning that it can reduce anxiety symptoms. For individuals experiencing temporary sleep loss due to anxiety, CBD may offer some therapeutic benefits.
There is also some evidence to suggest that CBD may alleviate post-traumatic-stress-induced nightmares and this has been investigated in veteran populations. However, sometimes the adverse effects of preparations that contain CBD and THC (such as dry mouth, dizziness, or headaches) can counteract these benefits.
A couple of studies have shown that cannabis may benefit those with restless legs syndrome, which is a condition typically caused by low iron levels in the brain. More research needs to be conducted in this area.
Lastly, there has only been one clinical trial to date that has investigated the effects of cannabis on obstructive sleep apnea. In this study, 10mg of dronabinol (a synthetic form of THC administered in capsule form) resulted in fewer respiratory events and less daytime sleepiness compared to the placebo. Cannabis may promote an opening of the airways during sleep, but future studies are needed to confirm this.
Our Take:
Cannabis is not the first-line treatment recommendation for any sleep disorder, and heavy use will likely impact sleep negatively. Research shows occasional use of CBD and THC products may improve sleep in the short term, but CBD-only products will likely have fewer unwanted side effects.
Will this benefit you?
There are limited options for treating subclinical sleep complaints. In other words, sleep that feels non-restorative, or even transient insomnia symptoms. A combination of healthy lifestyle practices is generally the best approach for supporting sleep. This includes morning light exposure, consistent sleep and wake times, staying active, eating well, and minimizing stress.
Still curious to try it? If you do, here’s what to keep an eye on:
The cannabis industry is poorly regulated and earlier this year, the FDA concluded that the framework provided for the supplement industry is not suitable for cannabis products. The rapid move to legalization across the United States suggests that a new framework will likely be put in place to better regulate consumer products in the near future. At present, it is difficult to guarantee that products contain the stated doses of THC and CBD. It is also difficult to determine whether any other contaminants are present, so care should be taken prior to consumption.
Lastly, most scientific research on cannabis products and sleep has had participants use oral capsules during studies. These may create different results than when cannabis is smoked or vaped, as is common in a real world setting and may increase the risk of airway inflammation.
References and additional materials:
History of Cannabis - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7605027/
The Endocannabinoid System - https://www.health.harvard.edu/blog/the-endocannabinoid-system-essential-and-mysterious-202108112569
Early research on cannabis and sleep - https://pubmed.ncbi.nlm.nih.gov/8569415/
More early research on cannabis and sleep - https://pubmed.ncbi.nlm.nih.gov/9813364/
Sleep Research Society Cannabis and Sleep Podcast - https://sleepresearchsociety.org/srs-podcast-cannabis-dosing-and-administration-for-sleep-a-systematic-review/
Endocannabinoids and aging - https://pubmed.ncbi.nlm.nih.gov/31368874/
Cannabis and sleep disorders - https://pubmed.ncbi.nlm.nih.gov/35537535/
FDA statement on cannabis industry regulation -https://www.fda.gov/news-events/press-announcements/fda-concludes-existing-regulatory-frameworks-foods-and-supplements-are-not-appropriate-cannabidiol
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