Cannabidiol (CBD) is emerging as a popular supplement. Its proponents claim that it is a safe anti-inflammatory that can improve conditions like irritable bowel disease, schizophrenia, anxiety and help you get more sleep. What does the science say? Read on to find out.
What is CBD?
Cannabidiol (CBD) is one of over 100 cannabinoids found in Cannabis sativa, the marijuana plant. CBD and THC are the two main active compounds found in the cannabis plant. They are also the best-studied and -recognized [1, 2].
Unlike THC, CBD is not psychoactive. It cannot cause the negative mental effects linked to THC, like paranoia, anxiety, and memory problems. Instead, some research suggests that it may naturally protect against the marijuana high [3, 4].
In early studies, CBD has shown promising benefits for people with a variety of hard-to-treat conditions .
- Prevents seizures in rare forms of epilepsy
- Reduces inflammation and may kill pain
- Potential for autoimmunity and neurological disorders
- Potential for some mental illness
- Reduces nausea and increases appetite
- Many possible benefits currently under investigation
- Well-tolerated with few reported side effects
- Not enough research in humans
- May cause drowsiness
- May be unsafe for people with compromised immune systems
- Potential drug interactions
Potential Health Benefits of CBD/Cannabidiol
Do not attempt to use CBD as an alternative to treatment by a medical professional. If you want to include CBD in your health management or treatment plan, talk to your doctor before doing so.
A prescription CBD oil is considered an effective anti-seizure medication. However, further research is needed to determine CBD’s other benefits and safety .
Likely Effective For
Many people claim that CBD helped them with seizures even when nothing else worked. The research backs them up: CBD may help reduce seizures in people with epilepsy who do not respond to drugs [7, 8].
In fact, in 2018, the FDA approved a CBD oral solution for the treatment of two rare forms of severe epilepsy. This approval is based on a robust base of evidence from the last several years of CBD research, but it is currently limited only to patients with Lennox-Gastaut syndrome and Dravet syndrome .
In a 3-month study of 23 children and young adults (3-26 years of age) with treatment-resistant epilepsy, those who received a purified 98% oil-based CBD extract experienced significantly fewer seizures. In 39% of participants, the incidence of seizures dropped by half .
In another trial of 214 children and adults with epilepsy, CBD was similarly linked to a reduction in seizures. The authors concluded that CBD was safe even at the maximum dose, which was double of the previous study .
In one survey, the parents of children who suffer from treatment-resistant epilepsy and use CBD were asked about the benefits of CBD. 19 parents were included, 84% of whom said that CBD reduced the frequency of seizures. Two parents said that CBD completely resolved seizures. Parents also reported improved alertness, sleep, and mood in their children. Some reported side effects were drowsiness and fatigue .
In 15 patients with epilepsy who didn’t respond to drugs, those who took 200 – 300 mg of cannabidiol per day over 4.5 months experienced fewer seizures. 7 out of 8 patients who took CBD improved, while only 1 patient in the placebo group did .
Possibly Effective For
We have receptors for cannabinoids in our whole body, but the first type (CB1) are very dense in the pain pathways of the brain, spine, and nerves. The second type (CB2) are more important for the immune system, but they are also involved in inflammation. According to some researchers, CBD may reduce both pain and inflammation through their actions on these receptors .
In a large analysis of 18 clinical trials, the authors concluded that cannabinoids strongly and safely reduced various types of chronic pain: neuropathic, arthritis, fibromyalgia, HIV, and multiple sclerosis pain. Another review of 16 studies found significant evidence of CBD’s benefits for people with chronic pain. The authors of this second review noted very little difference in tolerability between CBD and a placebo, meaning that CBD was not associated with side effects in a majority of studies; however, they note that the studies examining tolerability were of low quality [14, 16].
In several studies of people with multiple sclerosis and chronic pain, those taking a CBD/THC combination reported reduced pain. The combination was tolerated well and used regularly for up to 2 years [17, 18, 19, 20].
And importantly, according to one open-label study, CBD appears to be much less likely to cause tolerance long-term (after 2 years), unlike opioids and most other painkillers .
Although marijuana use can increase appetite and calorie intake, it has been linked to lower BMI, less obesity, and reduced likelihood of developing diabetes .
In one study of almost 5000 people, past and current marijuana users had lower fasting glucose and insulin levels (by 16%), lower waist circumference and BMI, lower insulin resistance (by 18%), and higher HDL. All these factors are connected to the onset of diabetes .
In another mouse study, CBD was associated with lower rates of destruction of insulin-producing cells in the pancreas. It was also linked to reduced inflammatory cytokines in these diabetic mice and a shift in the immune response from Th1 (autoimmune) to Th2. This result suggests a potential benefit for people with type I diabetes, in which autoimmunity is a major factor, but human studies have not yet been conducted .
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of CBD for any of the below-listed uses. Remember to speak with a doctor before taking CBD, and never use it in place of something your doctor recommends or prescribes.
4) Neurodegenerative Diseases
In a small study of 5 patients with movement disorders, those who took CBD had less uncontrollable muscle twitching, and higher doses had a stronger association. The patients received 100 to 600 mg of CBD per day over a 6-week period. 2 of the included patients with Parkinson’s disease experienced side effects (including a worsening of tremor) with doses over 300 mg per day, however .
In a study of 219 people with multiple sclerosis, those who took a combination of CBD and THC consistently reported fewer muscle spasms .
However, CBD combined with THC did not have any apparent effect on symptoms in a study of 17 patients with Parkinson’s disease .
Some other research suggests that CBD could protect brain cells from damage. In a cell study, neurons exposed to CBD suffered less damage from toxic substances and oxidative stress, which are responsible for many of the destruction caused by stroke and other forms of brain damage. This early study should soon be followed by animal and, eventually, human studies to further explore this benefit [33, 34].
Animal studies have produced largely encouraging results. In rodent models, CBD intake is associated with reduced brain damage, reduced beta-amyloid toxicity, and improved cognitive function, suggesting a potential future role in Alzheimer’s and Parkinson’s disease [35, 36, 37].
Animal research also suggests that CBD could protect the brain from the effects of stroke and reduced blood flow if the results can be repeated in humans. In cell studies, it was a stronger antioxidant than vitamin C (ascorbic acid) or vitamin E (α-tocopherol) [38, 39, 33].
5) Multiple Sclerosis Symptoms
According to some researchers, cannabinoids may relieve symptoms of multiple sclerosis (MS). In a study of 66 patients with MS and chronic pain, those who received a combination of CBD and THC reported less pain over 2 years. The patients determined the dosage by themselves, taking as much as they felt was needed to alleviate the pain .
In a study of 189 people with multiple sclerosis, those who used a combination of CBD and THC also reported reduced muscle tightness, pain, and sleep disturbances and improved bladder control [18, 19, 20].
In another study of 50 MS patients, those who took a CBD/THC combination reported somewhat reduced muscle tightness and improved sleep. Lower doses had a weaker association; the authors suggested that some MS patients in the study needed higher doses to get relief .
In 42 patients with acute schizophrenia, those who took CBD daily reported improvements of all symptoms after 4 weeks. The results were as strong for CBD as for a known antipsychotic drug, but CBD was tolerated much better. Interestingly, CBD was also linked to reduced breakdown of anandamide (blocked FAAH), which researchers suggest could explain the beneficial effects [46, 47].
While the psychoactive THC in cannabis seems to trigger psychotic episodes, especially in those with schizophrenia, CBD has opposite, antipsychotic effects. An increasing number of studies suggest that CBD could be an effective natural alternative to antipsychotic drugs, but with fewer side effects [48, 45].
According to some studies, people who experience psychosis may produce too much or not enough of their own cannabinoid signals. CBD binds to cannabinoid receptors less strongly than our internal cannabinoids; some researchers suggest that it could thus help re-establish a balance of cannabinoids in the brain. THC, on the other hand, is more potent than our internal cannabinoids (anandamide and 2-AG), which may explain how it triggers psychosis [44, 49].
Many animal studies have also supported an antipsychotic effect of CBD .
A single CBD dose of 400 mg was linked to reduced anxiety in a brain imaging study of 10 people with seasonal affective disorder. After consuming CBD, participants experienced reduced blood flow to parts of the limbic system that are often overactive in anxiety. At the same time, blood flow to another region important for cognition and motivation (the posterior cingulate cortex) increased [50, 51].
In a study of 10 healthy volunteers, those who took CBD felt less anxiety after the stressful task of public speaking. In 24 patients with social anxiety, taking CBD before public speaking was linked to reduced anxiety and discomfort and improved cognition [52, 53].
In another study, 8 volunteers experienced less anxiety when they took CBD with THC than when they took THC alone .
Future studies will explore the potential benefits of CBD for people with various types of anxiety, including panic disorder, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD) .
8) Rheumatoid Arthritis
As natural anti-inflammatory and antioxidant compounds, cannabinoids have the potential to provide relief of joint pain and swelling. In studies of arthritic animals, those given CBD suffered less joint destruction and slower progression of inflammatory disease [56, 57, 58].
In a trial of 58 people, people taking a CBD/THC combination (Sativex) reported reduced symptoms of rheumatoid arthritis. Over 5 weeks, this combination was associated with reduced pain during movement and at rest, improved sleep quality, and reduced inflammation. The study furthermore reported no serious adverse effects .
9) Nausea and Appetite
THC is an approved drug used to treat nausea and vomiting (dronabinol) in humans, but the clinical evidence for CBD in this function is limited .
One older study suggests that CBD and THC in combination are better than either alone for increasing appetite and reducing nausea. THC increases appetite, but its psychoactive effects are unpleasant to the patient. The authors suggest that CBD can reduce the psychoactivity of THC, without reducing appetite stimulation .
In animal studies, those given typical CBD doses vomited less and displayed fewer signs of nausea from toxic drugs. But given to the animals in very high doses, CBD appeared to increase nausea or become ineffective [61, 62].
Cannabis users with insomnia prefer strains much higher in CBD as a sleep aid. They are also less likely to become dependent on these high-CBD, low-THC strains, according to a survey of 163 adults purchasing medical cannabis. Furthermore, THC has been associated with worse sleep quality in the longer-term [63, 64].
CBD’s potential as a sleep aid could simply be due to its relaxing, anxiety-reducing effects .
11) Substance Use Disorders
Across the United States and around the world, a growing number of people suffer from opioid use disorder. According to promising early research, CBD may help these people break their dependence on opioid painkillers: people with chronic pain who use cannabis tend to take fewer opioid painkillers than those who do not use cannabis .
In a rat study, animals given CBD displayed less addictive behavior and were less likely to actively seek out morphine and heroin. The authors suggest that CBD could interfere with the brain’s reward system [66, 67].
12) Quitting Smoking
In a pilot study of 24 smokers, those who received cannabidiol smoked about 40% fewer cigarettes and did not report increased cravings for nicotine. Larger studies will be required to confirm whether CBD can help people quit smoking .
Animal & Cell Research (Lacking Evidence)
No clinical evidence supports the use of CBD for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
13) Inflammation and Autoimmunity
According to some researchers, CBD may be helpful in a variety of inflammatory and pain-associated conditions. It acts on the body’s cannabinoid receptors, which in turn regulate inflammation, balance the immune system, and protect from oxidative stress .
Our immune system has sensors for the cannabinoids our own body produces, as well as for those we take in. Some researchers believe that this internal cannabinoid system can become unbalanced in autoimmune disease and inflammation [57, 69].
CBD may act directly on immune cells to trigger a host of anti-inflammatory and antioxidant reactions:
Th1 and Th2 Dominance
In one study, asthmatic rats that received CBD had lower Th1 (IL-6 and TNF-alpha) and Th2 (IL-4, IL-5, IL-13) responses. CBD has not been tested in humans with asthma, so talk to your doctor before using it for this purpose .
A mouse study found an association between CBD and reduced markers of inflammation and pain. In immune cells, meanwhile, direct exposure to CBD led to decreased production of inflammatory signals (Th1: TNF-alpha, IFN-gamma, and IL-6; Th2: IL-4 and IL-8) [71, 72].
In one study, immune cells exposed to CBD expressed less IL-17 and had overall reduced Th17 activation. This result suggests a potential future role in suppressing Th17-dominant autoimmunity, but human studies have not yet been conducted, and much more research is required .
14) Heart Health
Some animal and cell studies have suggested a role for CBD in protecting the heart by relaxing blood vessels, reducing inflammation, and combating oxidative stress.
CBD was associated with more relaxed arteries and less damage to blood vessels in animal models of heart disease. It various studies of such animals, it was linked to more regular heart rhythms, reduced heart rate and blood pressure in response to stress, and reduced damage to the heart and brain from clogged blood vessels. Thus, some researchers believe that it could protect from heart attacks and stroke, but human trials have not yet been conducted [76, 77, 78, 79, 80].
In a cell study, platelets exposed to CBD clumped together less, reducing their potential to clog blood vessels. In white blood cells, CBD is linked to reduced inflammatory processes. Both of these effects could help explain its potential to improve heart health [81, 82].
In humans, CBD is much better studied for anxiety than for depression. Future studies will determine whether it has a role to play.
16) Inflammatory Bowel Disease
In another study, mice with IBD that were given CBD had reduced inflammation and normal gut movement. Tissues and cells exposed to CBD were less inflamed and displayed fewer signs of IBD-associated symptoms [89, 90, 91].
17) Antibacterial Activity
CBD showed some antimicrobial activity against methicillin-resistant Staphylococcus Aureus (MRSA), which often causes tricky, difficult-to-treat, hospital infections. This is one limited cell culture study, so it’s currently unclear how useful CBD could be against bacteria and other microbes, but research is ongoing .
18) Mad Cow Disease
In one fascinating study, mice were infected with a prion disease, a type of infectious protein that causes degeneration of the nervous system, and half were given CBD. Those in the CBD group lived almost a week longer than those in the control group .
Mad Cow and other prion diseases are notoriously difficult to treat, and they have no known cure. Future research will clarify whether CBD has a part to play in the emerging science of prions .
19) Bone Health
Although much less known, our bones also have little-researched receptors for cannabinoids.
In mice, CBD was linked to enhanced healing of broken limbs. Both CBD and THC were tested, but only CBD showed the potential to activate genetic pathways that increase collagen structure .
In a study on human skin tissue, exposure to CBD was linked to both decreased production of oils (sebum) and a reduced number of oil-producing glands. The skin tissue exposed to CBD also had fewer markers of inflammation. All of these effects would be very beneficial for people with acne. Hopefully, future human studies will determine whether CBD skin creams are effective against acne .
In one study, exposure to CBD was associated with reduced division of skin cells. Excessive division contributes to the development and symptoms of psoriasis; the authors of the study concluded that CBD has a potential role in future psoriasis treatments .
According to early research, CBD and other chemicals from cannabis show promising cancer-fighting properties. Interestingly, THC has also been studied for its potential against cancer, but its psychoactive effects in high doses are considered too severe.
In fact, cannabinoids similar to THC were first used to reduce nausea, pain, and improve appetite in cancer patients. Some synthetic cannabinoids are still used for this indication. More recently, researchers have uncovered the potential of natural cannabinoids like CBD and their possible role in combating the symptoms of cancer .
Overall, CBD is a non-psychoactive compound which is currently being investigated for cancer therapy. It might one day be used to improve the efficacy of standard treatments or as an anti-cancer substance on its own, though much more research will be required before that day comes. For the time being, ask your doctor about CBD as a complementary substance to determine whether it fits within your current treatment protocol .
Other cell studies suggest that CBD holds promise for fighting breast and prostate cancer. Some experts believe it directly reduces tumor size, alleviates pain, and can improve the effectiveness of conventional drugs [109, 110, 111].
Researchers have conducted many studies into the potential mechanisms of CBD against cancer. They believe that CBD probably works by starving cancer cells of energy, making them more sensitive to the body’s immune response, and by blocking a newly discovered cannabinoid-related cancer pathway (GPR55) [102, 112, 106, 108, 113, 114].
Although these studies are exciting, most of the research so far is limited to cells. It’s unknown if taking CBD could help combat cancer in humans.
CBD Side Effects & Safety
CBD is generally well tolerated and rarely produces side effects, even at high doses and when people use it for a long time .
Some people should take additional precautions, including:
- People with weakened immune systems, who should avoid or use it sparingly. In a cell-based study, CBD was associated with decreased activity of T and B immune cells. This implies that CBD may increase the likelihood of infections and worsen HIV, tumor growth, metastases, and asthma .
- People taking medication. CBD may decrease the activity of liver enzymes called cytochrome P450, responsible for metabolizing more than 60% of prescribed drugs. If you take prescription drugs, consult your doctor to rule out any interactions [116, 117].
People taking CBD have reported rare side effects, including a slight decrease in blood pressure, dry mouth, lightheadedness, and drowsiness. Combined with THC, it may interfere with learning and motivation [118, 119, 120].
Megadoses of CBD may trigger or worsen anxiety (via activation of TRPV1 receptors) .
Although CBD counters the THC high in normal doses, a monkey study suggests that large amounts of CBD could enhance the effects of THC. According to some researchers, high CBD doses mimic serotonin, which can boost THC’s psychoactive effects .
Since cannabinoids like CBD don’t mix well with water, they have to be formulated as oils. Furthermore, the amount of CBD that’s absorbed from the gut can vary, and large amounts may remain unabsorbed. New products like CBD/cannabinoid patches, nose sprays, and lozenges are being developed for better absorption .
CBD may be attractive to patients compared to synthetic cannabinoids and THC because it’s not psychoactive. Many people say they want to avoid the “high,” paranoia, and drowsiness that THC can cause .
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Cannabidiol (CBD) is a non-psychoactive cannabinoid extracted from the cannabis plant. It has been approved by the FDA to treat two rare forms of epilepsy; according to many early studies, it also has potential against autoimmunity, inflammatory conditions, anxiety, neurological disorders, substance use disorders, and more – though additional research is required to confirm these benefits.
CBD is generally well tolerated, but people with compromised immune systems or those taking prescription medications could be at risk of side effects. Always talk to your doctor before adding a new supplement to your daily health routine.