In studies, amounts vary from as low as 20 milligrams per day to up to 1,500 milligrams (mg) per day. The World Health Organization reports that dosages in clinical research studies typically range between 100 and 800 milligrams per day.
It is important to remember that this doesn’t mean that CBD isn’t effective. Many of the studies that were included in the review were small, had few participants, and were not randomized controlled trials.
It’s also important to remember that many products don’t contain just CBD on its own. There are three types of CBD available:
Is It Possible to Take Too Much?
Federal law prohibits the sale of products that contain more than 0.3% THC. States laws also vary, so you should always check with your state before buying CBD products online.
It may be helpful to take a broad-spectrum product since research suggests that CBD’s effects may be most beneficial when taken in conjunction with other cannabinoids, a phenomenon known as the entourage effect. CBD may also help mitigate some of the effects of THC.
How Much Should You Take?
CBD is just one of hundreds of different compounds found in the cannabis plant. While cannabis has been used in holistic medicine for many years, only recently have researchers begun to explore some of the medicinal purposes for CBD and other cannabinoids.
There have been a number of studies that suggest that CBD may have a number of different physical and mental health uses. However, more research is still needed to better understand the substance's potential applications and possible long-term side effects.
The treatment with CBD was in general well accepted, as judged by the clinicians’ and patients’ responses. Four patients declined CBD treatment because of religious or ethical concerns about the relation to cannabis. Nearly all patients easily provided informed consent once the nature of the treatment was explained. Most patients appreciated the opportunity to try something natural and avoid further or initial psychiatric medication use.
Wholeness Center is a large mental health clinic in Fort Collins, CO, that focuses on integrative medicine and psychiatry. Practitioners from a range of disciplines (psychiatry, naturopathy, acupuncture, neurofeedback, yoga, etc) work together in a collaborative and cross-disciplinary environment. CBD had been widely incorporated into clinical care at Wholeness Center a few years before this study, on the basis of existing research and patient experience.
Side effects and tolerability of CBD treatment were assessed through spontaneous patient self-reports and were documented in case records. Any other spontaneous comments or complaints of patients were also documented in case records and included in this analysis.
HAM-A = Hamilton Anxiety Rating Scale; PSQI = Pittsburg Sleep Quality Index.
These results must be interpreted cautiously because this was a naturalistic study, all patients were receiving open-label treatment, and there was no comparison group. Concurrent psychiatric medications were employed as in routine clinical care. This is both a limitation and strength, as very few publications exist in this population. Other researchers have noted that the large societal notoriety about cannabis and medical marijuana probably contributes to a larger-than-normal placebo effect.20 Any study that explores efficacy in this therapy probably will struggle with a potentially inflated placebo effect that will make these determinations more difficult. Likewise, the clinical population in this case series is skewed younger than typical for our clinic, and future studies could explore the possible selection bias inherent in this treatment option. Most patients were also taking psychiatric medications and receiving other mental health services, such as counseling, which limits the ability to make any causal links to CBD treatment. Clinical attrition is evident in the dataset. The reason for this might be related to CBD ingestion or not, so the overall component remains unclear. Furthermore, patients at our clinic often express a desire to reduce or to avoid use of psychiatric medications, which may contribute to an enhanced placebo effect or additional bias. The length of clinical monitoring may help to decrease this concern. However, the clinical data in this analysis show a trend toward clinically significant relief of anxiety upon the start of CBD treatment.
CBD has demonstrated preliminary efficacy for a range of physical and mental health care problems. In the decade before 2012, there were only 9 published studies on the use of cannabinoids for medicinal treatment of pain; since then, 30 articles have been published on this topic, according to a PubMed search conducted in December 2017. Most notable was a study conducted at the University of California, San Diego’s Center for Medicinal Cannabis Research that showed cannabis cigarettes reduced pain by 34% to 40% compared with placebo (17% to 20% decrease in pain).8 In particular, CBD appears to hold benefits for a wide range of neurologic disorders, including decreasing major seizures. A recent large, well-controlled study of pediatric epilepsy documented a beneficial effect of CBD in reducing seizure frequency by more than 50%.9 In addition to endorphin release, the “runner’s high” experience after exercise has been shown to be induced in part by anandamide acting on CB1 receptors, eliciting anxiolytic effects on the body.10 The activity of CBD at 5-HT1A receptors may drive its neuroprotective, antidepressive, and anxiolytic benefits, although the mechanism of action by which CBD decreases anxiety is still unclear.11 CBD was shown to be helpful for decreasing anxiety through a simulated public speaking test at doses of 300 mg to 600 mg in single-dose studies.12–14 Other studies suggest lower doses of 10 mg/kg having a more anxiolytic effect than higher doses of 100 mg/kg in rats.15 A crossover study comparing CBD with nitrazepam found that high-dose CBD at 160 mg increased the duration of sleep.16 Another crossover study showed that plasma cortisol levels decreased more significantly when given oral CBD, 300 to 600 mg, but these patients experienced a sedative effect.17 The higher doses of CBD that studies suggest are therapeutic for anxiety, insomnia, and epilepsy may also increase mental sedation.16 Administration of CBD via different routes and long-term use of 10 mg/d to 400 mg/d did not create a toxic effect on patients. Doses up to 1500 mg/d have been well tolerated in the literature.18 Most of the research done has been in animal models and has shown potential benefit, but clinical data from randomized controlled experiments remain limited.
Cannabidiol may hold benefit for anxiety-related disorders. Controlled clinical studies are needed.
Design and Procedures
The average age for patients with anxiety was 34 years (range = 18–70 years) and age 36.5 years for patients with sleep disorders (range = 18–72 years). Most patients with an anxiety diagnosis were men (59.6%, 28/47), whereas more sleep-disordered patients were women (64.0%, 16/25). All 72 patients completed sleep and anxiety assessments at the onset of CBD treatment and at the first monthly follow-up. By the second monthly follow-up, 41 patients (56.9%) remained on CBD treatment and completed assessments; 27 patients (37.5%) remained on CBD treatment at the third monthly assessment.
CBD was well tolerated, with few patients reporting side effects. Two patients discontinued treatment within the first week because of fatigue. Three patients noted mild sedation initially that appeared to abate in the first few weeks. One patient with a developmental disorder (aged 21 years) had to be taken off the CBD regimen because of increased sexually inappropriate behavior. The CBD was held, and the behavior disappeared. The behavior reappeared on redosing 2 weeks later, and the CBD regimen was formally discontinued. The treating psychiatrist thought this was related to disinhibition because the patient’s anxiety responded dramatically. One patient noted dry eyes. Reasons for patients not following-up at later assessment points are largely unknown but are probably because of standard attrition experienced in usual clinical practice. There was no evidence to suggest patients discontinued care because of tolerability concerns. The attrition rates were similar in nature and size to those found in routinely scheduled visits in this clinic.
To rate the overall quality of evidence for risk of bias, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used for each outcome of interest across all domains: methodological limitations of the studies, indirectness, imprecision, inconsistency and publication bias .
PubMed, Embase and Cochrane database were searched with all combinations of CBD and dosage in human studies. Reference lists of included studies were evaluated, and if needed, authors were contacted for further information.
PRISMA flow diagram of literature search and selection process. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses.
Study eligibility criteria
In one trial, 200 mg/day was administered for 13 weeks as an adjunct to current treatment to patients with type 2 diabetes. Compared to placebo, CBD did not have a significant effect on the level of high-density lipoproteins, the primary endpoint for this study . The effect of oral administration of CBD (20 mg/day for 8 weeks) on disease activity assessed by the Crohn’s disease activity index was evaluated in a small group of patients with long-standing Crohn’s disease taking concomitant medications. CBD had no effect on disease activity at the end of treatment and at 2 weeks follow-up . Irvin et al (2018) reported no effects of CBD-rich extracts (100 mg/day up to 250/day for 8 weeks) added to current treatment and administrated in the form of oral capsules to patients diagnosed with ulcerative colitis .