Product Review: CBD & Hemp Supplements
Initial Posting: 2/8/18
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What It Is:
- What is it? CBD (cannabidiol) is a compound derived from hemp and marketed as a supplement despite the U.S. FDA's position that CBD is not a dietary supplement.
- Does it work? CBD has been shown to reduce the frequency of certain types of seizures, and preliminary evidence suggests it may also help with anxiety, schizophrenia, and other conditions. However, all of these effects have involved large doses of CBD — hundreds of milligrams per day, which is more than in many marketed CBD supplements and products (See What It Is and What It Does).
- What did CL Find? ConsumerLab found the dose of CBD per suggested serving ranged 10-fold from 2.2 mg to 22.3 mg, and the cost to obtain 10 mg of CBD from each product ranged over 5-fold from 80 cents to $4.54. (See What CL Found and use the Results table to compare the amounts of CBD and other cannabinoids in products).
- Top Picks — ConsumerLab selected a Top Pick for People and a Top Pick for Pets based on top quality and value.
- What to look for? If you seek CBD, look for products that list the amount of CBD per serving. If a product lists only "cannabinoids" it may contain some CBD but you won't know how much. Products may still have significant amounts of CBD if they list "hemp extract" as an ingredient, but don't expect much CBD if "hemp oil" is the only ingredient. (See ConsumerTips)
- How much to take? Most of the research with CBD has involved high doses (several hundred milligrams daily). However, many CBD products on the market are lower dose and it is not clear if this dosing is effective. (See ConsumerTips: Dosage)
- Other Concerns: High-dose CBD can cause a range of side effects (particularly gastrointestinal) and affect certain medications. For details, see Concerns and Cautions.
Cannabidiol (CBD) and its precursor compound CBDa are dominant "cannabinoid" compounds found in hemp and cannabis (a hemp plant also known as marijuana). Unlike tetrahydrocannabinol (THC), which is another cannabinoid compound, CBD is not believed to be a psychoactive compound affecting perception and behavior.
What It Does:
NOTE: The effects described below are based on daily doses of hundreds of milligrams of CBD. Many CBD products on the market contain much lower amounts (providing tens of milligrams or less per day), and it is not known if these low doses are as effective as higher doses.
Much of the research with CBD has focused on the reduction of certain types of seizures. A placebo-controlled clinical trial found a high daily dose of CBD (20 mg per kg of body weight, i.e., hundreds of milligrams) to reduce the frequency of convulsions in a rare form of epilepsy known as Dravet syndrome in children and young adults, although it was also associated with a higher rate of adverse effects including diarrhea, vomiting, fatigue, pyrexia, somnolence, and abnormal results on liver-function tests (). Similarly, the same high daily dose reduced the number of drop seizures among people with treatment-resistant Lennox-Gastaut syndrome in a 3-month study. Seizures per month decreased 44% with CBD compared to 22% with placebo; however, again, those taking CBD also had a higher rate of adverse effects including diarrhea, somnolence, fever, decreased appetite, and vomiting ().
A preliminary trial found modest, dose-related improvements in symptoms of dystonia (involuntary muscle contractions) in five individuals taking between 100 mg and 600 mg per day of cannabidiol, however, there was a worsening of tremor and the ability to initiate movement in two of the individuals who also had Parkinson's disease ().
A study of high-dose CBD (1,000 mg per day) among adults with schizophrenia found that adding CBD rather than placebo to existing treatments for six weeks reduced psychotic symptoms and caused a trend, although not statistically significant, toward improved performance on cognitive tasks. In this study, CBD was given in two divided doses (morning and evening) and was well tolerated with no increase in adverse effects ().
Although laboratory studies and studies in animals suggest CBD may help reduce anxiety, there are only a few studies investigating these effects in people. For example, a small study in young healthy men found that a single, 400 mg dose of CBD taken as a capsule reduced self-reported anxiety (but also increased feelings of mental sedation), one hour after ingestion, compared to placebo (). A study that found CBD reduced anxiety with social speaking utilized a single dose of 600 mg of CBD given 90 minutes before speaking () and a similar study showed reduced anxiety using a dose of 300 mg (). In a 10 year old girl with anxiety and sleep disorders due to post traumatic stress disorder caused by sexual abuse, 25 mg of CBD taken at bedtime, and 6 mg to 12 mg of CBD sublingual spray taken as needed throughout the day for 5 months improved her anxiety and sleep to the extent that they were no longer classified as disorders (). Although no side effects were observed, it is important to note that there is concern that cannabinoids may affect brain development in children (See Concerns and Cautions).
A very small study among 15 men and women with a history of insomnia found that 160 mg of cannabidiol taken as a capsule 30 minutes before bedtime for one week significantly increased self-reported duration of sleep compared to placebo. Ten participants reported sleeping more than 7 hours after taking this dose of CBD, but when the same participants took a placebo, only six reported getting more than 7 hours of sleep. However, there was no decrease in the amount of time it took to fall asleep. Lower doses of CBD (40 mg and 80 mg) did not increase sleep time or reduce the amount of time it took to fall asleep (). None of the participants reported increased difficulty in waking or feeling sleepy upon awakening, compared to placebo.
Although there is some preliminary evidence that THC and, possibly other cannabinoids could potentially help to reduce interocular (eye) pressure in people with glaucoma, one study found that, four hours after ingestion, a single, sublingual dose of CBD (which also contained about 1 mg of THC) had no effect on interocular pressure, while a 40 mg dose of CBD (containing about 2 mg of THC) temporarily increased interocular pressure (; ). There do not appear to be longer-term studies, or studies investigating the effects of cannabidiol alone for glaucoma.
One study found that an oral spray containing THC and CBD reduced pain in people with rheumatoid arthritis (); however, a review of four short term clinical studies (including this one) investigating the effects of cannabinoids for the treatment of rheumatic diseases, including fibromyalgia syndrome, back pain, osteoarthritis and rheumatoid arthritis, concluded that there is "currently insufficient evidence to recommend cannabinoid treatments for management of rheumatic diseases pending further study." (). There do not appear to be any studies on the use of CBD alone for reducing pain in these conditions.
A few studies suggest that a combination of THC and CBD may be helpful for cancer-related pain; however, there do not appear to be studies on the effects of CBD alone for cancer-related pain (). (For more information about cannabinoids and cancer treatment, see the National Cancer Institute's about this topic.)
Creams, gels and lotions containing CBD are often promoted to treat pain, such as muscle or joint pain. CBD appears to be better absorbed through the skin than THC () and there is some evidence that in animals, creams and gels containing CBD may help reduce inflammation in conditions such as arthritis and multiple sclerosis (; ). However, there are no studies on the effects of topical CBD creams, gels or lotions in people.