Poor sleep is an increasingly common occurrence within the global population, with an estimated 10% of people affected by Insomnia. This sleep disorder is characterised by difficulties in getting to, and/or remaining, asleep. To be diagnosed with Insomnia, an individual must experience poor sleep that matches this description at least three times a week for a minimum of three months. Healthy sleep patterns are extremely important for both our mental and physical health, in addition to social functioning and our general quality of life. Therefore, consistent disruption to our sleep can have a significant negative impact on these areas of life. Furthermore, Insomnia has frequently been found to coexist with a number of medical and psychiatric disorders, including diabetes, cancer, chronic pain, depression, and anxiety.
The high prevalence of insomnia and significant negative effects of the disorder mean that effective treatment options are an important area of research; however, current therapies have several limitations. For example, while cognitive behavioural therapy (CBT) – a common first-line management – has been found to be effective, it can be difficult for some individuals to commit the time and energy necessary for success. In some cases, a limited number of medications have been approved for insomnia. While these medications may at least partially help to alleviate symptoms of Insomnia, they also carry a risk of side effects, including central nervous system depression, and dependency.
The limitations of current pharmacotherapy options for insomnia management mean that patients consistently turn to over-the-counter remedies and medications, such as diphenhydramine, melatonin, and chamomile. In addition, there is growing interest in whether medical products from the cannabis plant, in particular cannabidiol (CBD), have any role for individuals with insomnia.
The authors of a recent systematic review aimed to critically evaluate the existing literature regarding the potential of CBD in the management of Insomnia.
Design and Methods of the Study
Following a comprehensive search of various databases from inception to December 29, 2021, researchers identified 15 eligible studies. A further 19 studies were identified through citation searching, resulting in 34 studies eligible for inclusion in the systematic review. Eighteen of the included studies were clinical trials, including randomised controlled trials (n = 16) and non-randomised experimental studies (n = 2); 7 were cross-sectional studies, 5 were cohort studies, and 1 was a case report. Only 2 studies focused specifically on patients with insomnia, with the rest evaluating insomnia symptoms in patients with a number of other conditions (including cancer, multiple sclerosis, chronic pain, and fibromyalgia), cannabis/CBD users, and healthy adults.
Study Outcomes
Sleep quality was the primary outcome in 10 studies and a secondary outcome for the remaining 24 studies. Other primary outcome measures included pain, spasticity, anxiety, and fatigue. A number of sleep outcomes were utilised across the included studies. The most common were number of sleep disturbances per night, sleep quality, ability to fall asleep or stay asleep, and total sleep duration. All but two of the included studies also used subjective self-report questionnaires and two studies utilised polysomnography to objectively measure the impact of CBD on sleep outcomes.
CBD Preparations
A total of 19 studies investigated the effects of isolated or dominant CBD preparations on insomnia symptoms and 21 studies investigated nearly equal ratios of CBD and THC. These preparations were administered through various routes, including oromucosal or sublingual spray/drops, oral capsules/gelatine, inhalation, or topical applications. While doses ad application frequency varied, for studies that reported the quantity of CBD used, doses ranged from daily CBD doses of 2.5 mg to 330 mg.
Results of the Review
Of the studies that investigated the effects of CBD-only or CBD-dominant products (n = 19), seven studies directly assessed the difference in sleep outcomes compared with baseline or placebo. Four of these studies reported statistically significant improvements in insomnia symptoms, however, the other studies failed to find any improvement. Of the 21 studies that investigated the effects of CBD:THC products, only just over half of these were reported as statistically significant improvements in insomnia symptoms.
These results suggest that there are signals towards the effects of medical cannabis products in modulating sleep. However, the fact that the evidence base is largely inconclusive, means that further evidence from high-quality randomised controlled trials is necessary to determine the exact effects.
The authors noted that these findings are consistent with previous reviews examining the effects of CBD on sleep outcomes. Moreover, it should also be considered that, while the initial aim of this review was to examine the therapeutic potential of CBD for Insomnia, many of the included studies also assessed THC. It is, therefore, difficult to differentiate between the effects of CBD and THC in these patient populations.
