• The World Health Organization and other studies acknowledge that cannabidiol (CBD) is well-tolerated and has a good safety profile(1, 2). However, CBD may cause drowsiness, weight loss, hematologic abnormalities, increased liver enzymes(3), and dry mouth(4).
  • A study from Life Sciences mentioned CBD’s tendency to inhibit enzymes required to metabolize pharmaceutical drugs, leading to possible drug interactions and adverse reactions(5). 
  • A study published by Molecules noted that extremely high doses of CBD may cause liver injury in animal subjects(6). 
  • A 2020 research evaluated the risk of contamination in CBD oil. The authors expounded that heavy metal contamination was found in some CBD products, with lead as the most prevalent contaminant(7).
  • CBD products are not approved by the US Food and Drug Administration to diagnose, cure, mitigate, treat, or prevent any disease. Consumers should beware of purchasing and using these products as they may be mislabeled(8).


Cannabidiol has been studied for its potential therapeutic benefits. However, some studies also highlighted the possible side effects of CBD oil

First-time and long-time CBD users must consider possible drug interactions and adverse effects. Risks associated with CBD production are also a determining factor when choosing a safe CBD brand.

Comprehensive studies have been shared publicly to help individuals learn how CBD may affect humans and animals. These findings can also be helpful in one’s decision-making process.

Human Studies on CBD Side Effects

Some CBD studies have progressed to human trials. These effects were reported and observed after initial administration or prolonged use of CBD.

According to a review shared by Cannabis and Cannabinoid Research, some side effects were observed among human subjects undergoing CBD treatment for epilepsy(9)

The side effects mentioned in the 2017 review were drowsiness, diarrhea, and changes in appetite. In some cases, CBD may cause elevated liver enzymes and irregularities in red blood cell volume(10)

Some other adverse effects reported by subjects who used cannabis strains with high-CBD content include dizziness, lightheadedness, irritability, or confusion(11).

CBD side effects may vary per user. Scientists during clinical trials observed the following adverse effects.

Reduced Weight

In a study, researchers observed the prevalence of weight loss among subjects who received 20 mg/kg of CBD per day compared with the placebo group(12).

During the controlled trial, volunteers were divided into two groups: a placebo group and Epidiolex group. 

Epidiolex is an antiepileptic medication containing CBD as the active ingredient. It is also the first CBD-comprised drug approved by the US Food and Drug Administration (FDA). 

The drug contains 100 milligrams (mg) of CBD per millimeter (ml). The recommended dosages vary from 5 to 20mg per kilogram (kg) per day(13).

The epilepsy drug is used on children diagnosed with severe forms of epilepsy, such as Dravet syndrome and Lennox-Gastaut syndrome

Hematologic Abnormalities

Another side effect observed during the Epidiolex controlled trial was hematologic abnormalities. About 30% of Epidiolex-treated patients developed a new form of anemia(14). 

During the trial, the subjects experienced a decrease in hemoglobin (proteins in red blood cells) and hematocrit (volume of red blood cells). 

Dry Mouth

Saliva production inhibition (dry mouth) has been linked to the use of cannabinoids, including CBD. The side effect is commonly reported among CBD and cannabis users(15)

However, additional studies are needed to learn how CBD may cause dry mouth

Drowsiness

Studies have shown that drowsiness is a common side effect of CBD(16).

In an Epidiolex controlled trial, 32% of subjects taking 10 to 20mg/kg doses of CBD per day experienced sedation and somnolence (state of drowsiness or desire to sleep)(17).

Due to these side effects, those who are taking CBD are advised by experts not to drive or operate machinery. 

Liver Toxicity

Animal and human studies have shown CBD’s potential to cause liver toxicity(18)

For example, in Epidiolex’s controlled trials, liver enzymes were elevated in 5% to 20% of patients. Increased liver enzymes is a sign of liver inflammation.

Side Effects of CBD Use When Pregnant

There is a lack of studies on how CBD alone may affect pregnancy in humans. Most studies involving cannabinoids and pregnancy are focused on cannabis use.

Scientists are studying the impact of cannabis use among women of childbearing age. According to the National Pregnancy and Health Survey organized by the National Institute of Drug Abuse (NIDA), the prevalence of cannabis use among women in 2016 was 2.9%(19). 

Researchers found that women exposed to cannabinoids during the first trimester caused an increased risk of neuroblastoma in their offspring(20).

Neuroblastoma is caused by immature nerve cells. This form of cancer typically arises from adrenal glands(21).

Another study observed an increased frequency in mutant lymphocytes in mothers exposed to cannabis. Lymphocytes are white blood cells crucial to a human’s immune system(22)

Mutated lymphocyte activities have been compared to cancer cells(23). These findings discussed the exposure to a variety of cannabinoids, not only CBD.

There is no comprehensive study that discusses how pregnant and breastfeeding mothers taking CBD may affect their infants. 

However, the US Food and Drug Administration (FDA) released a warning against the use of cannabis among pregnant or breastfeeding mothers due to THC(24)

THC is a cannabinoid that causes psychoactive effects. Marijuana has been known to contain high concentrations of THC

The FDA cited a study that mentioned how mothers’ marijuana use had been associated with low birth weights, premature births, and stillbirths(25).  

The agency also warned that THC could go into the bloodstream and transfer into breastfeeding mothers’ breast milk(26).

Although these findings refer to cannabis and not only CBD, some CBD oil products still contain traces of THC

Animal Studies on CBD Side Effects 

Many comprehensive animal studies help scientists understand how CBD may affect humans. These studies also help veterinarians learn how CBD may work for pets and livestock.

The side effects of CBD may vary per species. Typical reactions observed among multiple species are elevated liver enzymes(27), sedation(28), embryo-fetal mortality, male reproductive system abnormalities, and central nervous system (CNS) inhibitions(29)

Central Nervous System Inhibition

In an animal study, rhesus monkeys were given 150 to 300mg/kg CBD(30). After 30 minutes, the animals demonstrated CNS inhibitions, such as tremors, sedation, depression, and prostration (physical or mental exhaustion).

Rat models also displayed a sub-lethargic condition, which also decreased their appetite and reduced stimuli response. This observation came after scientists administered an extremely high dose of CBD (738 mg/kg to 2460 mg/kg)(31).

A 2019 study from Animals explained how CBD administration affected dogs and cats. While the dogs did not demonstrate any signs of CNS inhibition, one of eight cats in the study displayed shaking and excessive licking(32).

Dry Mouth

A study from Experimental Biology and Medicine noted the inhibition of salivary glands in rat models due to anandamide (AEA), a form of endocannabinoid(33).

Endocannabinoids are cannabinoids produced by animals and humans, while phytocannabinoids are produced by plants.

The difference between endocannabinoids and phytocannabinoids (which are found in CBD products) is its source. 

Both of these cannabinoids have an affinity to endocannabinoid receptors in the mammalian body.

The study mentioned that AEA triggers the cannabinoid receptors in rats, decreasing saliva secretion(34)

Biochemical studies have shown that cannabinoids, such as CBD, may enhance AEA signaling. This hypothesis means that CBD may have the ability to increase AEA production(35).

Liver Toxicity

Some studies have shown that CBD may positively affect liver function in mouse models(36)

In a recent study, researchers indicated that high doses of CBD may cause hepatotoxicity(37). Hepatotoxicity (liver damage) is a medical condition caused by an overdose of a chemical, medicine, herb, or supplement. 

The 2019 study posted by Molecules used human-quantity doses of CBD on rat models. These doses were a total of 246 mg/kg, 738mg/kg, and 2,460mg/kg in a span of 10 days(38)

The 738mg/kg rat models displayed a significant increase in liver-to-body ratio. Meanwhile, rat models that received the 2,460mg/kg dose had elevated oxidative stress levels(39)

Although the authors expounded that the doses used in the experiment do not apply to real-life scenarios, the conclusion still posed as a reminder to practice caution when taking CBD.

Side Effects of CBD in Pregnant Animals

Studies have shown that consuming CBD may cause developmental defects.

A recent review has mentioned how prenatal exposure to CBD led to increased eye defects and cranial malformation in rat models(40). The authors noted that the CBD dose given to the rats was in the therapeutic range. 

Moreover, scientists discussed how perinatal exposure to cannabinoids, such as CBD and THC, may alter the rats’ brains(41)

This brain alteration was discovered by scientists using retrieved brain tissue samples from rat offsprings. The offsprings’ mothers were exposed to CBD, delta 9-tetrahydrocannabinol (delta 9-THC), and delta 8-THC(42).

Risks of CBD Oil

Possible Drug Interactions

Enzymes are proteins in the body that accelerate chemical reactions. They also play a vital role in body functions, like digestion and respiration. 

In humans, the cytochrome 450 enzyme is essential for detoxifying the body from foreign chemicals and metabolizing drugs. 

The CYP450 has more than 50 classifications(43). However, only six of these classifications have roles in metabolizing 90% of known pharmaceutical drugs

These enzymes are CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5(44).

According to a study shared by Life Sciences, CBD inhibits the activity of CYP3A4 and CYP3A5 enzymes(45)

Blocking these enzymes may result in the ineffectiveness of drugs, including diazepam (Valium), alprazolam (Xanax), estradiol (Estrace), sildenafil (Viagra), and atorvastatin (Lipitor)(46). 

Research has shown that CBD may also inhibit CYP1A2 and CYP2C9 enzymes, making CBD a potent competitive inhibitor of warfarin(47)

Warfarin is a blood-thinning agent used for deep vein thrombosis (DVT) and pulmonary embolism(48).

Moreover, the makers of Epidiolex have warned against the concomitant use of CBD and valproate (an epilepsy drug). 

According to Epidiolex’s prescribing information manual, studies have shown that combining Epidiolex (which contains CBD as an active ingredient) and valproate may cause liver injury(49)

CBD has been shown to be safe when combined with another epilepsy medication, clobazam(50). Still, caution is advised when combining CBD and other medications.

CBD’s blocking of enzymes has been compared to the effects of grapefruit. The FDA published an article explaining how grapefruit can also interfere with medications by blocking the CYP3A4 enzyme(51)

Contamination

Good manufacturing practices are essential in creating high-quality CBD oil products. 

If manufacturers do not take extra precautions, the CBD product may become contaminated with bacteria, pesticides, herbicides, residual solvents, heavy metals, and other harmful substances. 

Consuming harmful substances, like pesticides and heavy metals, can cause various illnesses, such as lung damage, diarrhea, high blood pressure, hair loss, and memory problems(52)

Consuming microbial contaminants has been reported to cause food poisoning(53).

A study shared by Veterinary Medicine has discovered that four out of 29 CBD-rich cannabis products were contaminated with heavy metals(54).

Unfortunately, no regulating body has been assigned to regulate CBD companies’ product outcomes. Most of the time, products are manufactured and go straight into retail. 

Thus, when searching for CBD products, individuals must check the product’s third-party laboratory report or certificate of analysis (COA).

The COA determines if the product contains contaminants and harmful chemicals. CBD brands with readily available COAs are preferable compared to brands that are not transparent with their COAs.

Mislabeling

Consumers must also practice caution when shopping for CBD products due to possible mislabelling. 

The FDA recently reported that some CBD brands were untruthful about their CBD concentrations. For instance, the agency also called out several CBD brands for making claims linked to the coronavirus disease 2019 (COVID-19)(55)

Although CBD products may be legally sold in the US, regulations prohibit CBD from being marketed as a pharmaceutical drug or dietary supplement.

According to a research paper posted by JAMA, over 70% of CBD products sold online are not labeled accurately(56)

This finding was discovered after researchers purchased over 80 CBD products online. Mislabeling was mostly related to the products’ concentration. 

Consumers must practice caution when shopping for CBD products. Taking the extra step of checking the product concentration can help prevent risks associated with mislabelling.

Many CBD brands have published COAs indicating the cannabinoid content in their products. THC levels are prohibited from exceeding 0.3% in all CBD products

Checking the COA reduces the risks of consuming more THC than intended.

Inaccurate Dosing

Due to the lack of universal dosage recommendations, there is a risk of consuming too much CBD. High CBD dosage may increase the risk of liver injury(57). 

More research is needed to determine the appropriate CBD dosage for specific health issues. Studies have shown that a high CBD dose may not necessarily provide better effects.

The Brazilian Journal of Psychiatry demonstrated that CBD has an inverted U-shaped dose-response curve. 

During the study, researchers put healthy volunteers in an anxiety-inducing environment (public speaking). The CBD dosages provided to the subjects were 150mg, 300mg, and 600mg(58).

The 300mg CBD dose provided positive results, while 150mg and 600mg doses failed to produce any significant improvements(59).

This dose-response curve means lower doses, in some cases, may be more effective than higher doses.

When taking CBD for the first time, one must start with a low dose. Once the body gets used to taking CBD, one may gradually increase the dosage.

A review published by the British Journal of Clinical Pharmacology collected over 1,038 scientific articles regarding CBD. 

Based on their research, the authors determined that a CBD dose of <1 and 50 mg of CBD per kilogram per day is enough to provide significant improvements in anxiety, psychotic symptoms, and seizures(60).

CBD’s Effects on Medical Conditions: What Research Says

Although CBD’s clinical value in treating various health conditions is still in question, many researchers have already presented significant hypotheses. 

CBD’s Antipsychotic Effects on Psychosis

Studies have shown that CBD may possess antipsychotic effects. In a case study, scientists have explored CBD’s potential to help patients with psychotic disorders, including schizophrenia(61).

According to a review shared by Psychopharmacology, CBD was used as monotherapy on a schizophrenia subject for four weeks. Results of the study showed that oral CBD administration may reduce psychotic symptoms(62).

There are less than promising results in another case series involving three patients with treatment-resistant schizophrenia. Out of the three patients, only one showed improvements in symptoms of psychosis(63).

More comprehensive case studies are needed to verify CBD’s clinical value. 

CBD’s Antiepileptic Effects on Seizures 

Research has established CBD’s effectiveness in treating epilepsy.

During a trial phase, Epidiolex (an epilepsy drug) was used in a double-blind controlled-trial involving 120 children and young adults(64)

The subjects, who had medication-resistant Dravet syndrome, were divided into two groups: the placebo group and the CBD-treated group.

In addition to the trial treatment, both groups also started a standard epileptic treatment(65). The CBD-treated group demonstrated a reduction in convulsive seizures (from a median frequency of 12.4 to 5.9) after a fourteen-week treatment period. 

This result was significantly better than the placebo group’s results (from a median frequency of 14.9 to 14.1)(66)

In an analytical report from the American Academy of Neurology, it was noted that CBD-treatment effectively reduced the frequency of seizures among Dravet syndrome patients(67)

The authors added that long-term CBD use, combined with standard epileptic treatment, further reduced the seizures’ frequencies without safety concerns(68). 

CBD’s Anxiolytic Effects on Anxiety and Insomnia

A review from Neurotherapeutics explored CBD’s effects on various anxiety disorders, including social anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress disorder(69).

The authors cited preclinical studies that observed how rat models behave in a stress-induced environment. Scientists suggested that CBD may provide anxiolytic (antianxiety) and anxiogenic (anti-panic) effects after administration(70). 

A separate study has also acknowledged CBD for its anxiolytic effects on humans(71). A study released in the Permanente Journal demonstrated CBD’s potential to improve anxiety scores. 

The study also recognized CBD’s ability to enhance sleep quality(72). In some cases, CBD caused a drowsiness effect that may be beneficial for individuals with insomnia. 

Human volunteers who took CBD reported improved sleep quality within the first month of treatment(73).

CBD’s Antidepressant Effects on Depression and Bipolar Disorders

A study published in the Frontiers in Immunology investigated the antidepressant properties of CBD(74)

According to the study, CBD had been demonstrated to activate serotonin receptors in animal models. The activation of these receptors may increase glutamate (neurotransmitter) release.  

Researchers suspected that disturbance in the glutamatergic (glutamate) system may be connected to mood disorders, such as depression and bipolar disorders(75).

Further research is needed to determine how CBD may contribute to neurotransmitter activities and potentially provide antidepressant effects on humans. 

CBD’s Anti-inflammatory Effects on Chronic Pain

A study shared by Therapeutics and Clinical Risk Management suggested that cannabinoids, such as CBD and THC, may potentially alleviate difficult-to-treat pain(76). 

According to the authors, the cannabinoids have neuroprotective antioxidant properties. These properties contribute to the cannabinoids’ potential in alleviating neuropathic pain caused by health conditions, including multiple sclerosis and rheumatoid arthritis(77). 

A study published in the European Journal of Pain also discussed how transdermal CBD application may also provide anti-inflammatory effects and pain relief for arthritis(78)

According to the researchers’ findings, CBD gel administration reduced the knee joint circumference progression in rat models with induced-arthritis(79)

CBD’s Vasorelaxant Effects on Cardiovascular System

According to a review from the British Journal of Pharmacology, CBD has the potential to protect the vascular system from damage and reduce vascular tension(80)

Evidence suggested how CBD may have therapeutic effects on the cardiovascular system.

CBD has been shown to increase blood flow and reduce the infarct size (tissue death) of animal stroke models(81).  

A subsequent study demonstrated how a single dose of CBD oil lowered the blood pressure of healthy volunteers(82)

The researchers divided the volunteers into two groups. One group received a placebo, while the other received 600mg of CBD. 

In the study, the volunteers went through several stress tests, followed by blood pressure examinations. The volunteers’ resting blood pressure was also measured.

Results showed that the CBD group had lower blood pressure compared to the placebo group(83). The effect was attributed to CBD’s ability to block inflammation in human coronary artery cells. 

The study continued to acknowledge CBD’s vasorelaxant properties(84). However, additional studies are needed to verify how CBD may help with cardiovascular disorders. 

CBD’s Neuroprotective Effects on Neurodegenerative Disorders

CBD’s possible effects are limited when it comes to neurodegenerative diseases. 

Questions remain whether CBD may positively impact human neurodegenerative disorders, such as multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease.

CBD’s neuroprotective, neurotransmission, and neurogenesis (new neurons) properties were acknowledged in a study posted by the British Pharmacological Society(85)

According to the study, CBD’s neuroprotective properties may help relieve symptoms of multiple sclerosis and Parkinson’s disease. These same properties may also slow the progression of Alzheimer’s disease(86).

CBD has also been shown to alleviate neurodegenerative symptoms.

An article published by Frontiers in Neurology expounded CBD’s ability to reduce spasticity, reduce pain, and improve mobility may help individuals with multiple sclerosis(87).

In a subsequent study, researchers evaluated CBD’s efficacy in reducing tremors of Parkinson’s disease. The patients received 300mg of CBD before they were placed in an environment designed to induce tremors(88)

Results showed that CBD may help reduce anxiety scores and tremors amplitude(89).

CBD’s Analgesic Effects on Cancer

Cannabinoids, such as CBD and THC, have been shown to provide pain relief in some cancer patients(90)

According to studies, CBD treatment combined with THC is not more effective than opioids when alleviating pain in advanced cancer patients. 

Due to the side effects caused by opioids, researchers are looking to cannabinoids as an alternative analgesic treatment(91)

In another study published by Phytomedicine, researchers demonstrated how high-CBD cannabis extracts reduced the rapid multiplication of tumor cells in a xenograft model of colon cancer(92)

According to the study, the mechanism involves the cannabinoids’ ability to activate CB1 and CB2 receptors. This activity led to the attenuation of colon carcinogenesis(93).

Apoptosis or cell death has a vital role in cancer treatment(94). Apoptosis occurs when enzymes program the cells to die (after being attacked by immune cells). 

Dysfunction in apoptosis may lead to many forms of cancer(95)

According to a study shared by Oncotarget, CBD treatment could initiate apoptosis (cell death) and make cancer cells more susceptive to radiation therapy without affecting healthy cells(96). The demonstration was conducted on glioblastoma cancer cells.

CBD is not an accepted standard treatment for cancer. Although researchers have used nabiximol (1:1 CBD and THC) in cancer studies(97), the drug is currently at phase 3 clinical trial in the US(98)

Nabiximol is specially formulated to treat patients with multiple sclerosis(99)

Further studies are needed to verify CBD’s efficacy in treating pain caused by cancer. 

How CBD Works 

The endocannabinoid system (ECS) is composed of cannabinoid receptors found in humans and other mammals. These receptors respond to endogenous and exogenous cannabinoids

This response has a neuromodulatory function, which may play a role in influencing the central nervous system (CNS) and the immune system(100).

The ECS has two primary cannabinoid receptors, CB1 receptors and CB2 receptors. 

The CNS has an abundance of CB1 receptors. Meanwhile, CB2 receptors are found in the peripheral nervous system and organs(101). CB2 receptors are also expressed in the immune system(102).

The CB1 receptor’s presence in the CNS had prompted many scientists to study how cannabinoids may modulate pain signals(103).

The British Journal of Pharmacology published a study attributing CBD for having a direct and indirect influence on CB1 receptors(104)

Although the receptor affinity is low, CBD’s indirect influence on the CB1 receptors has resulted in several studies on its effects on the central nervous system.

Surgical Neurology International released a study discussing the neuroprotective properties of phytocannabinoids, including CBD(105). Researchers suspected that CBD may attenuate brain damage caused by neurodegenerative diseases(106).

This hypothesis was supported by a recent review posted by the Frontiers in Pharmacology. The authors listed the mechanisms of CBD on CB1 and CB2 receptors and their pharmacological actions(107).

CBD acts as a CB1 and CB2 antagonist causing an antispasmodic (anti-spasms) effect. Spams are a symptom of several neurological disorders, such as dystonia and multiple sclerosis(108)

Moreover, scientists have demonstrated how CBD provided neuroprotective effects on animal models of Parkinson’s disease (PD). The study showed that CBD reduced oxidative stress by acting on the receptors, resulting in decreased neuronal cell death(109).

The authors also expounded how CBD may help in reducing pro-inflammatory cytokines, therefore improving memory alterations. This observation was based on CBD counteracting the Amyloid-beta (Aβ)-induce microglial activation(110)

Aβ is a peptide often linked to causing Alzheimer’s disease(111). Some studies mentioned that Aβ plaques are the first sign of the disease(112).

Aside from CB1 and CB2, CBD has been known to trigger receptors outside the ECS.

The study indicated how CBD caused increased adenosine levels in the brain, resulting in suspected neuroprotection and decreased brain inflammation(113). Adenosine is an organic compound that affects the transfer of neurons in the brain. 

Neurodegenerative diseases linked to brain inflammation are Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, and multiple sclerosis(114).

Moreover, CBD’s action towards CB1 and CB2 receptors may influence the ECS into providing therapeutic benefits such as antipsychotic, anticonvulsant, anxiolytic, and sleep-promotion(115)

Furthermore, CBD has been known to behave as an inverse agonist towards the CB2 receptor, causing anti-inflammatory effects(116).  

When CB2 is triggered, this stimulates an anti-inflammatory response, reducing pain and inflammation. This anti-inflammatory response may help alleviate health conditions, such as arthritis, Crohn’s disease, and inflammatory bowel syndrome (IBS)(117)

How to Choose High-Quality CBD Oil

The CBD industry has created a standard in terms of offering high-quality CBD oil. To ensure product safety and quality, legitimate CBD brands provide customers with the certificate of analysis (COA). 

The COA is a third-party laboratory report that indicates the potency and concentration of the CBD product. Furthermore, the COA verifies if the products’ concentration is consistent with the label. 

The COA also indicates if the product is safe for human and animal consumption. The report verifies if products are free from pesticides, herbicides, solvent residues, heavy metals, and other contaminants.

Here are tips to consider when looking for high-quality CBD oil:

  • Always verify the safety of CBD products by checking the updated COA of each batch. 
  • Individuals may check if the laboratory is verified by the International Standardization Organization (ISO) and International Electrotechnical Commission (IEC). These certifications mean that the laboratories follow pharmaceutical standards.
  • Search for CBD brands that have certifications and accreditations from regulatory bodies. Some brands are certified organic by the United States Department of Agriculture (USDA) or have the Good Manufacturing Practice (GMP) stamp of approval. 
  • Check the CBD company’s Better Business Bureau (BBB) rating. Companies with A ratings from BBB usually provide excellent customer service and good quality products.

How to Take CBD Oil 

CBD may be administered orally, sublingually, topically, and through inhalation. The most common CBD product is the CBD oil tincture, which may be consumed sublingually. 

Individuals may take the dropper and use it to apply CBD oil under the tongue. Some CBD users like to add the tincture to food and drinks.

Tinctures may also come in a variety of flavors. Meanwhile, some brands offer variants without additional flavors, allowing naturally-occurring terpenes from hemp to provide a distinct, earthy flavor. 

Individuals who prefer an easier administration may opt for CBD capsules or softgels. They are swallowed with a glass of water. 

Another oral method to administer CBD is through oral sprays. Brands have created a way for individuals to deliver a dose of CBD by spraying the product into the mouth. 

CBD users who prefer taking CBD through edibles may choose CBD gummies. The CBD content in gummies is lower than that of tinctures and capsules, making it a good option for first-time CBD users. 

Another common CBD administration is through inhalation. Individuals who prefer this method may opt for CBD vape pens and CBD oil inhalers. 

CBD administration has been known to deliver plasma concentrations in 10 minutes or less(118). However, using vape products may cause some side effects, such as chest pains, allergic reactions, and chemical irritation(119).

Topical CBD administration is available through CBD creams, CBD balms, CBD gels, and CBD lotions. The topical administration method is recommended for health conditions linked to muscle aches, joint inflammation, joint pain(120), or skin disorders(121)

The Medical Community’s Position on CBD

The only FDA-approved CBD drug is Epidiolex, which is used to treat epilepsy.

Other FDA-approved drugs contain synthetic THC and CBD. These drugs are used to reduce vomiting and nausea caused by health problems, including cancer(122)

Nabiximol, a drug containing almost equal amounts of CBD and THC, can be legally prescribed to multiple sclerosis patients in the United Kingdom (UK)(123)

However, in the US, nabiximol has to go through several controlled trials before being approved for medical use. 

Despite growing public acceptance, CBD’s status in the medical community remains questionable. 

FAQs

What is CBD Oil?

Cannabidiol (CBD) is a naturally-occurring cannabinoid found in cannabis plants (Cannabis sativa), such as hemp and marijuana. 

Other cannabinoids found in hemp and marijuana are tetrahydrocannabinol (THC), cannabigerol (CBG), cannabichromene (CBC), and cannabinol (CBN).

THC is the cannabinoid responsible for the psychoactive effects induced by cannabis. In the United States, hemp growers are prohibited from using strains containing more than 0.3% THC.

Manufacturers use an extraction method to separate the cannabinoids from hemp extracts. During this process, certain cannabinoids, such as THC, may be further reduced to comply with regulations.

The remaining cannabinoids are suspended in a carrier oil, such as hempseed oil, olive oil, or medium-chain triglyceride (MCT) oil. 

CBD oil products are formulated to contain high concentrations of CBD. Depending on the type of CBD oil, other cannabinoids may also be found in the product.

What are the Types of CBD Oil

Full-spectrum CBD oil consists of all the cannabinoids present in hemp plants, such as CBD, CBN, CBG, and THC. When an individual consumes the cannabinoids, this creates a synergy of the compounds known as the “entourage effect.”  

The entourage effect implies that the benefits of the cannabinoids are greater when taken together rather than individually.

Broad-spectrum CBD oil contains all the cannabinoids found in hemp, except for THC. Some CBD users prefer using broad-spectrum CBD oil to avoid THC’s detection in their system, while others prefer not to take THC due to intolerability. 

The third type of CBD product is the CBD isolate (pure CBD). Some CBD companies sell CBD isolate in a powder form, while others suspend the compound in a carrier oil. 

CBD isolates are preferred by individuals who do not want other cannabinoids in their system. 

Is CBD Psychoactive? 

CBD, as monotherapy, is non-psychoactive. However, when CBD is combined with other compounds, the effects are relative to the formula and how individuals respond to the product.

Individuals who take CBD products may experience lethargy or drowsiness. Furthermore, CBD products that exceed the legal amount of THC may also cause some undesired psychoactive effects.

Is CBD Addictive? 

CBD is non-addictive. Scientists have studied CBD for its potential to relieve withdrawal symptoms of opioid addiction(124)

Substance Abuse: Research and Treatment published a review that recognized CBD for its ability to control neuronal circuits involved in drug addiction(125). The authors cited animal studies that suggest CBD may be useful as an interventional treatment for opioids, cannabis, and tobacco addiction.

Is CBD Safe?

Studies have established that CBD has a favorable safety profile(126). Despite the several side effects, CBD was acknowledged for improving quality of life, especially in patients with epilepsy(127)

Furthermore, the World Health Organization reported that CBD is well-tolerated and safe(128)

The 2018 United States Farm Bill legalized the cultivation of industrial hemp containing less than 0.3% THC

Legitimate CBD products are created using hemp cultivars approved by the United States Department of Agriculture. These cultivars are bred to contain high CBD  and very low THC (no more than 0.3%).

GW Pharmaceuticals, the pharmaceutical company behind the creation of Epidiolex, has announced that the drug is no longer covered by the Controlled Substances Act. 

This announcement came after the United States Drug Enforcement Administration (DEA) sent a notice of “descheduling” to the pharmaceutical company(129).

The DEA also indicated that only CBD products exceeding 0.3% THC could be considered a schedule 1 controlled substance(130).

Still, the legality of CBD remains ambiguous. Although products are currently legally sold throughout the United States, CBD brands are prohibited from making any health claims. 

CBD products are also banned from being marketed as a dietary supplement or a food supplement.

The CBD industry is highly unregulated. The FDA has expressed public health concerns due to some companies’ questionable practices. 

How Is CBD Oil Different From Hemp Oil?

Hemp oil does not necessarily mean that it contains CBD. Hemp oil may be extracted from hemp flowers, stalks, and seeds. Manufacturers creating hemp oil may or may not use hemp strains that are high in CBD. 

Meanwhile, hempseed oil has very low traces of cannabinoids.

CBD oil comes from hemp flowers and stalks, which have high cannabinoid content.

Individuals who want to take advantage of CBD’s potential therapeutic properties should buy products that specify its CBD content.

Is CBD Oil the Same as Marijuana?

CBD oil uses hemp strains containing less than 0.3% THC.

Marijuana strains offered by licensed dispensaries can contain 25% to 28% THC(131). These are the cannabis strains that cause psychoactive effects

According to US federal law, only 11 US states legally allow the sale and use of marijuana(132)

Conclusion

Although CBD has been observed to provide potential health benefits for various medical conditions, the cannabinoid may still cause some side effects, especially in high doses

Individuals planning to take CBD into their daily regimen must be well-informed about the possible side effects and reactions when combined with pharmaceutical drugs. 

Furthermore, individuals must also be aware of the risks associated with bad practices from illegitimate CBD brands.

Before buying CBD, consumers must always check if the CBD product has an updated certificate of analysis.

One must also consult with a licensed physician or a licensed healthcare provider before deciding to try or take CBD. 


  1. The World Health Organization. Cannabidiol: A Critical Review Report. Retrieved from https://www.who.int/medicines/access/controlled-substances/CannabidiolCriticalReview.pdf
  2. Iffland, K., & Grotenhermen, F. (2017). An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. Cannabis and cannabinoid research, 2(1), 139–154. https://doi.org/10.1089/can.2016.0034
  3. Epidiolex Prescribing Information. Retrieved from https://www.epidiolex.com/sites/default/files/pdfs/0820/EPX-03645-0820_EPIDIOLEX_%28cannabidiol%29_USPI.pdf
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  7. Wakshlag, J. J., Cital, S., Eaton, S. J., Prussin, R., & Hudalla, C. (2020). Cannabinoid, Terpene, and Heavy Metal Analysis of 29 Over-the-Counter Commercial Veterinary Hemp Supplements. Veterinary medicine (Auckland, N.Z.), 11, 45–55. https://doi.org/10.2147/VMRR.S248712
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  13. Ibid.
  14. Ibid.
  15. The Mayo Clinic. Is CBD Safe and Effective? Op cit.
  16. Iffland, K., & Grotenhermen, F. (2017). Op cit.
  17. Epidiolex Prescribing Information. Op cit.
  18. Ewing, L. E., (2019). 
  19. Dong, C., Chen, J., Harrington, A., Vinod, K. Y., Hegde, M. L., & Hegde, V. L. (2019). Cannabinoid exposure during pregnancy and its impact on immune function. Cellular and molecular life sciences : CMLS, 76(4), 729–743. https://doi.org/10.1007/s00018-018-2955-0
  20. Ibid.
  21. Ibid.
  22. Molecular Biology of the Cell. 4th edition. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK26921/.
  23. Turner, D. R., Grist, S. A., Janatipour, M., & Morley, A. A. (1988). Mutations in human lymphocytes commonly involve gene duplication and resemble those seen in cancer cels. Proceedings of the National Academy of Sciences of the United States of America, 85(9), 3189–3192.
  24. The US Food and Drug Administration. What You Should Know About Cannabis Including CBD When Pregnant or breastfeeding. Retrieved from https://www.fda.gov/consumers/consumer-updates/what-you-should-know-about-using-cannabis-including-cbd-when-pregnant-or-breastfeeding#:~:text=FDA%20strongly%20advises%20against%20the,during%20pregnancy%20or%20while%20breastfeeding.&text=Cannabis%20and%20Cannabis%2Dderived%20products,products%20appearing%20all%20the%20time.
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  27. Ewing, L. E., (2019). Op cit.
  28. Kogan, L., Schoenfeld-Tacher, R., Hellyer, P., & Rishniw, M. (2019). US Veterinarians’ Knowledge, Experience, and Perception Regarding the Use of Cannabidiol for Canine Medical Conditions. Frontiers in veterinary science, 5, 338. https://doi.org/10.3389/fvets.2018.00338
  29. Huestis, M. A., Solimini, R., Pichini, S., Pacifici, R., Carlier, J., & Busardò, F. P. (2019). Cannabidiol Adverse Effects and Toxicity. Current neuropharmacology, 17(10), 974–989. https://doi.org/10.2174/1570159X17666190603171901
  30. Ibid
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  32. Silver R. J. (2019). The Endocannabinoid System of Animals. Animals : an open access journal from MDPI, 9(9), 686. https://doi.org/10.3390/ani9090686
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  34. Ibid
  35. Leweke, F. M., Piomelli, D., Pahlisch, F., Muhl, D., Gerth, C. W., Hoyer, C., Klosterkötter, J., Hellmich, M., & Koethe, D. (2012). Cannabidiol enhances anandamide signaling and alleviates psychotic symptoms of schizophrenia. Translational psychiatry, 2(3), e94. https://doi.org/10.1038/tp.2012.15
  36. Avraham, Y., Grigoriadis, N., Poutahidis, T., Vorobiev, L., Magen, I., Ilan, Y., Mechoulam, R., & Berry, E. (2011). Cannabidiol improves brain and liver function in a fulminant hepatic failure-induced model of hepatic encephalopathy in mice. British journal of pharmacology, 162(7), 1650–1658. https://doi.org/10.1111/j.1476-5381.2010.01179.x
  37. Ewing, L. E., (2019). Op cit.
  38. Ibid
  39. Ibid
  40. Argueta, D. A., Ventura, C. M., Kiven, S., Sagi, V., & Gupta, K. (2020). A Balanced Approach for Cannabidiol Use in Chronic Pain. Frontiers in pharmacology, 11, 561. https://doi.org/10.3389/fphar.2020.00561
  41. Walters, D. E., & Carr, L. A. (1988). Perinatal exposure to cannabinoids alters neurochemical development in rat brain. Pharmacology, biochemistry, and behavior, 29(1), 213–216. https://doi.org/10.1016/0091-3057(88)90300-0
  42. Ibid
  43. AFFP. The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects. Retrieved from https://www.aafp.org/afp/2007/0801/p391.html#:~:text=Cytochrome%20P450%20enzymes%20are%20essential,enzymes%20being%20CYP3A4%20and%20CYP2D6.
  44. Ibid.
  45. Yamaori, S., Ebisawa, J., Okushima, Y., Yamamoto, I., & Watanabe, K. (2011). Op cit.
  46. AFFP. The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects. Op cit.
  47. Grayson, L., Vines, B., Nichol, K., Szaflarski, J. P., & UAB CBD Program (2017). An interaction between warfarin and cannabidiol, a case report. Epilepsy & behavior case reports, 9, 10–11. https://doi.org/10.1016/j.ebcr.2017.10.001
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  50. Geffrey, A.L., Pollack, S.F., Bruno, P.L. and Thiele, E.A. (2015), Drug–drug interaction between clobazam and cannabidiol in children with refractory epilepsy. Epilepsia, 56: 1246-1251. doi:10.1111/epi.13060
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  60. Millar SA, Stone NL, Bellman ZD, Yates AS, England TJ, O’Sullivan SE. A systematic review of cannabidiol dosing in clinical populations. Br J Clin Pharmacol. 2019;85(9):1888-1900. doi:10.1111/bcp.14038
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  62. Ibid.
  63. Ibid.
  64. Devinsky, O, Cross, J.H.,Laux, L., Marsh, E., Miller, I., Nabbout, R., Scheffer, I., Thiele, E., Wright, S. (2017) Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. N Engl J Med 2017; 376:2011-2020. DOI: 10.1056/NEJMoa1611618
  65. Ibid.
  66. Ibid.
  67. Long-Term Safety and Efficacy of Cannabidiol (CBD) Treatment in Patients with Dravet Syndrome (DS): 3-Year Interim Results of an Open-Label Extension (OLE) Trial (GWPCARE5) (439)
  68. Ibid.
  69. Blessing, E. M., Steenkamp, M. M., Manzanares, J., & Marmar, C. R. (2015). Cannabidiol as a Potential Treatment for Anxiety Disorders. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 12(4), 825–836. https://doi.org/10.1007/s13311-015-0387-1
  70. Ibid.
  71. Shannon, S., Lewis, N., Lee, H., & Hughes, S. (2019). Cannabidiol in Anxiety and Sleep: A Large Case Series. The Permanente journal, 23, 18–041. https://doi.org/10.7812/TPP/18-041
  72. Ibid.
  73. Ibid.
  74. Crippa, J. A., Guimarães, F. S., Campos, A. C., & Zuardi, A. W. (2018). Translational Investigation of the Therapeutic Potential of Cannabidiol (CBD): Toward a New Age. Frontiers in immunology, 9, 2009. https://doi.org/10.3389/fimmu.2018.02009
  75. Jun, C., Choi, Y., Lim, S. M., Bae, S., Hong, Y. S., Kim, J. E., & Lyoo, I. K. (2014). Disturbance of the glutamatergic system in mood disorders. Experimental neurobiology, 23(1), 28–35. https://doi.org/10.5607/en.2014.23.1.28
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  77. Ibid.
  78. Hammell, D. C.,(2016). Op cit.
  79. Ibid.
  80. Stanley, C., & O’Sullivan, S. E. (2014). Vascular targets for cannabinoids: animal and human studies. British journal of pharmacology, 171(6), 1361–1378. https://doi.org/10.1111/bph.12560
  81. Ibid.
  82. Jadoon, K. A., Tan, G. D., & O’Sullivan, S. E. (2017). A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study. JCI insight, 2(12), e93760. https://doi.org/10.1172/jci.insight.93760
  83. Ibid.
  84. Ibid.
  85. Fernández‐Ruiz, J., Sagredo, O., M. Ruth Pazos, García, G., Pertwee, R., Mechoulam, R., Martínez‐Orgado, J., (2012). Cannabidiol for neurodegenerative disorders: important new clinical applications for this phytocannabinoid? British Pharmacological Society https://doi.org/10.1111/j.1365-2125.2012.04341.x
  86. Ibid.
  87. Rudroff, T., & Sosnoff, J. (2018). Cannabidiol to Improve Mobility in People with Multiple Sclerosis. Frontiers in neurology, 9, 183. https://doi.org/10.3389/fneur.2018.00183
  88. de Faria, S. M., de Morais Fabrício, D., Tumas, V., Castro, P. C., Ponti, M. A., Hallak, J. E., Zuardi, A. W., Crippa, J., & Chagas, M. (2020). Effects of acute cannabidiol administration on anxiety and tremors induced by a Simulated Public Speaking Test in patients with Parkinson’s disease. Journal of psychopharmacology (Oxford, England), 34(2), 189–196. https://doi.org/10.1177/0269881119895536
  89. Ibid.
  90. Fallon, M. T., Albert Lux, E., McQuade, R., Rossetti, S., Sanchez, R., Sun, W., Wright, S., Lichtman, A. H., & Kornyeyeva, E. (2017). Sativex oromucosal spray as adjunctive therapy in advanced cancer patients with chronic pain unalleviated by optimized opioid therapy: two double-blind, randomized, placebo-controlled phase 3 studies. British journal of pain, 11(3), 119–133. https://doi.org/10.1177/2049463717710042
  91. Ibid.
  92. Romano, B., Borrelli, F., Pagano, E., Cascio, M. G., Pertwee, R. G., & Izzo, A. A. (2014). Inhibition of colon carcinogenesis by a standardized Cannabis sativa extract with high content of cannabidiol. Phytomedicine : international journal of phytotherapy and phytopharmacology, 21(5), 631–639. https://doi.org/10.1016/j.phymed.2013.11.006
  93. Ibid.
  94. Wong R. S. (2011). Apoptosis in cancer: from pathogenesis to treatment. Journal of experimental & clinical cancer research : CR, 30(1), 87. https://doi.org/10.1186/1756-9966-30-87
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  96. Ivanov VN, Wu J, Wang TJC, Hei TK. Correction: Inhibition of ATM kinase upregulates levels of cell death induced by cannabidiol and γ-irradiation in human glioblastoma cells. Oncotarget. 2019;10(65):7012–7013. Published 2019 Dec 10. DOI:10.18632/oncotarget.27352.
  97. Fallon, M. (2017). Op cit.
  98. US Food and Drug Adminsitration. Public Health Focus. FDA Regulation on Cannabis and Cannabis-derived Products. Retrieved from https://www.fda.gov/news-events/public-health-focus/fda-regulation-cannabis-and-cannabis-derived-products-including-cannabidiol-cbd
  99. About Sativex (nabiximols). Retrieved from https://www.mstrust.org.uk/a-z/sativex-nabiximols
  100. Lu, H. C., & Mackie, K. (2016). An Introduction to the Endogenous Cannabinoid System. Biological psychiatry, 79(7), 516–525. https://doi.org/10.1016/j.biopsych.2015.07.028
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  102. Turcotte, C., Blanchet, M. R., Laviolette, M., & Flamand, N. (2016). The CB2 receptor and its role as a regulator of inflammation. Cellular and molecular life sciences : CMLS, 73(23), 4449–4470. https://doi.org/10.1007/s00018-016-2300-4
  103. Manzanares, J., Julian, M., & Carrascosa, A. (2006). Role of the cannabinoid system in pain control and therapeutic implications for the management of acute and chronic pain episodes. Current neuropharmacology, 4(3), 239–257. https://doi.org/10.2174/157015906778019527
  104. Pertwee R. G. (2008). The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. British journal of pharmacology, 153(2), 199–215. https://doi.org/10.1038/sj.bjp.0707442
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  106. Cassano, T., Villani, R., Pace, L., Carbone, A., Bukke, V. N., Orkisz, S., Avolio, C., & Serviddio, G. (2020). From Cannabis sativa to Cannabidiol: Promising Therapeutic Candidate for the Treatment of Neurodegenerative Diseases. Frontiers in pharmacology, 11, 124. https://doi.org/10.3389/fphar.2020.00124
  107. Ibid.
  108. Cassano, T., (2020). Op cit.
  109. Ibid.
  110. Ibid.
  111. Murphy, M. P., & LeVine, H., 3rd (2010). Alzheimer’s disease and the amyloid-beta peptide. Journal of Alzheimer’s disease : JAD, 19(1), 311–323. https://doi.org/10.3233/JAD-2010-1221
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  113. Ibid.
  114. Stephenson, J., Nutma, E., van der Valk, P. and Amor, S. (2018), Inflammation in CNS neurodegenerative diseases. Immunology, 154: 204-219. doi:10.1111/imm.12922
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  116. Ibid.
  117. Turcotte, C., Blanchet, M. R., Laviolette, M., & Flamand, N. (2016). The CB2 receptor and its role as a regulator of inflammation. Cellular and molecular life sciences : CMLS, 73(23), 4449–4470. https://doi.org/10.1007/s00018-016-2300-4
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