In a review of related literature on the safety of cannabidiol (CBD), several studies commonly reported generally mild adverse effects of CBD in various medical conditions including tiredness, diarrhea, and changes of appetite/weight(1). 

Different researchers also discovered CBD’s potential therapeutic mechanisms for diabetes, chronic pain, Alzheimer’s disease(2), Parkinson’s disease(3), post-traumatic stress disorder (PTSD)(4), anxiety disorders, schizophrenia(5), high blood pressure(6), severe forms of epilepsy, and multiple sclerosis.

The research, mostly including animal studies(7), compared CBD’s side effects versus placebo. However, more clinical trials are warranted to determine any conclusive benefits and long-term effects

Several CBD products have yet to undergo evaluation from the US Food and Drug Administration (FDA) for their efficacy, proper dosage, possible drug interactions, risks, and side effects. 

As such, the FDA prohibits manufacturers from marketing CBD products as medicine or even dietary supplements(8). These regulations are in place to protect potential consumers from unproven uses of CBD.

Is CBD Oil Safe for Children? 

Since the emergence of Epidiolex, CBD oil for kids has become a popular treatment option among parents of children with anxiety and symptoms of autism spectrum disorder(9).

The FDA approved the use of Epidiolex in June 2018. This oral solution made from CBD was approved as an effective treatment for Lennox-Gastaut syndrome and Dravet syndrome(10)

Epidiolex is the first FDA-approved drug that contained a purified, cannabis-derived substance for seizures associated with severe and rare forms of childhood epilepsy.

The solution’s approval is also supported by significant scientific evidence(11).

According to Doris Trauner, MD, professor of neurosciences and pediatrics at the University of California San Diego School of Medicine and a doctor at San Diego’s Rady Children’s Hospital, parents have reported significant improvement in their children with anxiety(12) and sleep problems(13) when given 12mg to 25mg doses of CBD once daily.

Meanwhile, Orrin Devinsky, MD, director of New York University Langone’s Comprehensive Epilepsy Center in New York City, says there is growing evidence that CBD can ease anxiety. This disorder may be accompanied by attention-deficit/hyperactivity disorder (ADHD)(14).

Charlotte Figi’s situation is one of the famous case studies of CBD use in children. She was an American girl from Colorado who took CBD to help with her Dravet syndrome. The strain of medical cannabis, “Charlotte’s Web,” was named after her(15)

Despite anecdotal evidence, the guidelines for CBD oil use in children remain unclear. According to Dwight Blake, a mental health counselor at Long Island Psychotherapy and Counseling in Westbury, New York, parents should consider starting their children with low CBD doses and gradually increasing the dosage to achieve desired results(16).

Furthermore, Dr. Paul Mitrani, a pediatrician and clinical director at the Child Mind Institute, encourages parents to wait for further research before considering turning to CBD to treat their children’s mental health disorders(17).

Consulting a pediatrician experienced with cannabis is the best course of action for parents who want to include CBD in their child’s diet, especially if these children are already taking other medications.

What is CBD Oil?

The World Health Organization (WHO) explains that CBD is a naturally occurring cannabinoid found in cannabis plants(18). In most cases, CBD is derived from the hemp plant, although it can also come from the marijuana plant.

High-concentration CBD hemp rarely contains delta-9-tetrahydrocannabinol (THC), which is the compound that gives marijuana its psychoactive effects and gets individuals high” High-quality CBD is non-toxic and considered safe for pets and humans alike.

According to FDA Principal Deputy Commissioner Amy Abernethy, MD, PhD, the increase in the number of CBD products may be owed to the changes in state law. The Farm Bill of 2018 also removed hemp from the definition of marijuana according to the Controlled Substances Act(19).

The law redefined hemp as a cannabis derivative with very low concentrations (no more than 0.30% on a dry weight basis) of THC.

CBD products are still subject to the same laws and requirements as other FDA-regulated products.

Health Benefits of CBD Oil

While several studies look into CBD oil’s potential health benefits, individuals must remember that CBD products are still subject to FDA laws and requirements(20).

It must also be stressed that one should seek professional medical advice before including CBD oil in their diet.

Despite being subject to strict FDA regulation, CBD and cannabis were found promising in the treatment of various medical conditions.

Cancer Treatment

In a 2019 study by the University of Korea, researchers observed that CBD’s anticancer protein killed tumor cells. The researchers studied the synergistic effects of CBD with the cancer-destroying protein called TRAIL (TNF-related apoptosis-inducing ligand).

The study concluded that TRAIL and CBD created apoptosis, or cell death, separately in colorectal cancer cells. The researchers also found that combined, both CBD and TRAIL reduced cancer cells significantly(21).

Alzheimer’s Disease Treatment

In 2019, researchers in South Korea compiled studies of marijuana for Alzheimer’s disease. The researchers selected and analyzed nine studies for review(22).

The studies’ results implied that CBD components of cannabis have the potential to treat and prevent Alzheimer’s disease.

In the research, the CBD components suppressed the main factors that cause Alzheimer’s disease.

The study also suggested that CBD was more effective when used together with THC than when the individual cannabinoid was used alone.

PTSD Treatment

In 2019, a study examined the effects of CBD in treating PTSD symptoms among 11 adult patients(23). For eight weeks, researchers assessed PTSD symptom severity every four weeks.

The researchers found that the participants’ PTSD symptoms have reduced upon the oral administration of CBD. However, the authors concluded that further research and more clinical trials were warranted.

High Blood Pressure Treatment

In a 2017 study, researchers looked into CBD’s cardiovascular effects and investigated if the substance reduces blood pressure in humans(24).

Data showed that among nine healthy male volunteers, subjects who took CBD had lower blood pressure, increased heart rate, decreased stroke volume, and a blunted forearm skin blood flow.

The study concluded that CBD’s acute administration reduced a human’s resting and high blood pressure. Still, further research is required to establish CBD’s role in treating cardiovascular disorders.

Side Effects of CBD

CBD generally has a good safety profile(25). However, low-quality CBD oil products that are untested may contain harmful contaminants and lead to adverse effects(26).

CBD side effects include(27):

  • Dry mouth
  • Tiredness
  • Changes in weight/appetite
  • Diarrhea
  • Sedation
  • Fatigue

Some harmful contaminants in CBD oil may include heavy metals, pesticides, molds, mycotoxins, and synthetic cannabinoids (SCs).

Synthetic Cannabinoids

By the definition of the Centers for Disease Control and Prevention (CDC), synthetic cannabinoids (SCs) are potentially toxic man-made chemicals that are intended to function similarly to marijuana, but actually don’t(28).

SCs have the capability to attach themselves to some of the same receptors that process CBD and THC, but likely many others as well and in different ways than THC and CBD, thus explaining their potential harmful effects(29).

A clinical study published by the College of Psychiatric and Neurologic Pharmacists explains that SCs are psychoactive substances(30).

These substances are gaining popularity because of their availability and lack of detection by standardized drug tests.

According to research, SCs have resulted in some of the following health conditions:

  • Fatal coronary artery thrombosis
  • Arrhythmias
  • Myocardial infarction
  • Sudden cardiac death
  • Psychosis
  • Suicidal tendencies
  • Seizures
  • Acute tubular necrosis
  • Intracranial hemorrhage
  • Anxiety disorders
  • Drowsiness
  • Agitation

The study further explained that synthetic cannabinoid products are unpredictable due to unregulated manufacturing processes and the variety of their active ingredients.

Although some users may perceive SCs as safer alternatives to medical marijuana, some SCs are more potent when they interact with the cannabinoid receptors and could result in more severe toxicities, threatening public health and wellness.

Healthcare providers must know about the range of toxicities related to SC use. 

Potential Interaction with Existing Medication

CBD oil may interact with some medications, including selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant, and benzodiazepines(31). CBD may cause more drowsiness or other side effects like elevated liver enzymes with certain medications.

A 2019 study on the potential drug events and drug-drug interactions involving CBD use suggested starting with a low CBD dose if consumers are already taking medications(32).

In a 2018 study, researchers investigated the interaction between CBD and tacrolimus (TAC), an immunosuppressive drug(33).

The study explained that CBD has the potential to inhibit the metabolizing enzymes  CYP3A4 and CYP2C19. Inhibition of metabolizing enzymes may alter the disposition of many common drugs (what happens to the drug after entering the body), potentially resulting in more adverse effects and toxicities(34).

Researchers conducted the study on a 33-year old female with refractory epilepsy. The patient was receiving TAC for treating her interstitial nephritis, a kidney disorder.

The patient was stable on TAC but showed signs of TAC toxicity after receiving CBD.

Thus, individuals should take caution and consult a doctor before taking CBD along with their existing medications. They must closely monitor the responses of cannabis to certain drugs.

Lab Reports

Ideally, a company that offers CBD products is transparent with the third-party laboratory results of its items. Customers can verify a product’s potency through its lab results or certificate of analysis (COA).

A COA is a document that a third-party laboratory issues a CBD company to confirm a product’s contents.

The laboratories that conduct purity tests must comply with good manufacturing practices (GMP).

GMP certification implies a quality approach to manufacturing, ensuring that companies eliminate or minimize instances of contamination, mixups, and errors(35).

Cannabinoid Analysis Issues

There are numerous methods for analyzing cannabinoids, yet there is still no standard agreed upon and analytic method used to test accuracy and suitability.

According to a study in the Netherlands on Dutch CBD oil, researchers collected 46 different cannabis oil samples directly from patients and analyzed them for their cannabinoid content(36).

Arno Hazekamp conducted this study, which Karger published in 2018. Karger publishes peer-reviewed journal articles for open access(37).

The obtained samples were homemade or purchased from an online store. Label information on the CBD or THC content was available for 21 of the 46 products (46% of all samples).

According to analysis, the cannabinoid content varied from the content declared on the label. Around 57% of the samples had a THC content of over 1%, while 39% of the oil samples contained THC only(38).

Such discrepancies were also found in homemade and commercially obtained products, according to Hazekamp(39).

How Does CBD Work?

Through cannabinoid receptors, CBD can trigger the body’s endocannabinoid system (ECS)(40). The ECS exists in all animals, except insects(41).

The ECS is vital in maintaining homeostasis or a state of balance within the human body, as explained in a 2018 study published in the Journal of Young Investigators(42).

Some brands have CBD products for pets. Still, the FDA has not approved medical cannabis use among pets and recommends owners consult with their veterinarians.

How to Take CBD

Consumers can take CBD in a variety of ways.

Sublingual Application

Sublingual use of CBD requires users to apply a dropper’s amount of CBD tincture under the tongue to absorb.

A 2020 study looking into the ways of delivering CBD found that sublingual delivery of the complexation of CBD with beta cyclodextrin (β-CD) (used to improve solubility) produced superior bioavailability compared to oral dosage forms of CBD in rabbits(43).

Bioavailability refers to the extent that a substance becomes available to the intended biological destination(44).


CBD oil can be infused in food and drink for individuals to ingest.

Some brands produce CBD gummies and capsules for controlled dosing of CBD.


Vaping products are also available for convenience and easier CBD intake.

A 2016 study found that vaping CBD reduces the harmful byproducts of combustion from smoking while utilizing CBD’s potential therapeutic properties(45).

Still, individuals must consider the potential risks associated with vaping. Some reports have linked vaping to lung disease(46).

Topical Administration

Companies may utilize CBD’s anti-inflammatory properties by infusing CBD into topicals, such as balms, salves, and lotions.

There is some new evidence that transdermal application of CBD could be effective in relieving nerve pain(47).

Types of CBD

CBD may come in full-spectrum, broad-spectrum, or isolate product variations.

Full-spectrum CBD contains the entire range of cannabinoids, including a federally allowed amount of THC, flavonoids, terpenes, and fatty acids.

Even if this type of CBD contains only trace amounts of THC, continuous use of full-spectrum or any CBD product may still result in failed drug tests.

Broad-spectrum CBD contains almost the same naturally occurring cannabinoids and other components of full-spectrum CBD, except THC.

Meanwhile, CBD isolates are made from purified CBD fully isolated from the hemp plant.

Best Advice on Choosing CBD Oil

Before purchasing a CBD product, consumers must take into account the following factors to choose the best CBD oil for their needs:

  1. CBD consumers should ensure that labeling is proper and accurate by checking the COA. They should also check for dosage instructions.
  2. CBD consumers should examine each CBD product and its contents.
  3. Examine where and how the CBD product was manufactured.
  4. Analyze the potential therapeutic effects.
  5. Analyze the risks that may result from product use by understanding the item’s contents.
  6. Watch out for misleading labels.
  7. Look out for potentially harmful and deadly contaminants.
  8. Research the third-party labs associated with a CBD brand.

Hemp-derived products are federally legal in all 50 states with few exceptions, per the 2018 Farm Bill, allowing the growth, cultivation, manufacture, and processing of hemp plants(48).

The Farm Bill of 2018 redefined hemp plants as Cannabis sativa plants with less than 0.30% of THC content by dry weight.

This update removed industrial hemp from the list of Schedule I drugs under the Controlled Substances Act.

Schedule I drugs are classified as substances with a potential for abuse and no accepted medical benefits.

As such, CBD oil is legal for sale and consumption at the federal level if derived from qualifying hemp.

State laws may have varying degrees of restrictions regarding the distribution and possession of CBD.


Although there are several studies on CBD’s health benefits, there is not enough evidence to support its overall long-term safety and efficacy for conditions other than certain seizure disorders.

Different people may have unique reactions to CBD. Existing medications also have the potential to interact with CBD. This interaction is a concern that individuals interested in CBD use should consider.

Although CBD is federally legal in the United States, people should consult with medical professionals before taking CBD.

  1. 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. 
  2. Kim, S. H., Yang, J. W., Kim, K. H., Kim, J. U., & Yook, T. H. (2019). A Review on Studies of Marijuana for Alzheimer’s Disease – Focusing on CBD, THC. Journal of pharmacopuncture, 22(4), 225–230.
  3. Rieder C. R. (2020). Cannabidiol in Parkinson’s disease. Revista brasileira de psiquiatria (Sao Paulo, Brazil : 1999), 42(2), 126–127.
  4. Elms, L., Shannon, S., Hughes, S., & Lewis, N. (2019). Cannabidiol in the Treatment of Post-Traumatic Stress Disorder: A Case Series. Journal of alternative and complementary medicine (New York, N.Y.), 25(4), 392–397.
  5. Boggs, D.L., Surti, T., Gupta, A. et al. The effects of cannabidiol (CBD) on cognition and symptoms in outpatients with chronic schizophrenia a randomized placebo controlled trial. Psychopharmacology 235, 1923–1932 (2018).
  6. 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.
  7. 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.
  8. FDA Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD). U.S. Food & Drug Association. 2020 Oct 1. Retrieved from
  9. Peachman, RB. (2019, Feb 26). Can CBD Help Your Child? Retrieved from
  10. FDA Approves First Drug Comprised of an Active Ingredient Derived from Marijuana to Treat Rare, Severe Forms of Epilepsy. U.S. Food & Drug Administration. 2018 June 25. Retrieved from
  11. EPIDIOLEX (cannabidiol) oral solution.
  12. Peachman, RB. (2019, Feb 26). Op cit
  13. Shannon S, Opila-Lehman J. Effectiveness of Cannabidiol Oil for Pediatric Anxiety and Insomnia as Part of Posttraumatic Stress Disorder: A Case Report. Perm J. 2016;20(4):16-005. doi:10.7812/TPP/16-005.
  14. Peachman, RB. Op cit.
  15. Maa, E., & Figi, P. (2014). The case for medical marijuana in epilepsy. Epilepsia, 55(6), 783–786.
  16. Blake, D. (2020, Jan 13). The Best CBD Oil for Kids in 2020 (It’s uses, benefits and Industry Trends). Retrieved from
  17. Martinelli, K. (2019, April 26). CBD: What Parents Need to Know. Retrieved from
  18. Cannabidiol (CBD) Pre-Review Report. World Health Organization. 2017 November. Retrieved from
  19. Hemp Production and the 2018 Farm Bill. U.S. Food & Drug Administration. 2019 July 25. Retrieved from
  20. Ibid
  21. Kim, J. L., Kim, B. R., Kim, D. Y., Jeong, Y. A., Jeong, S., Na, Y. J., … Lee, D.-H. (2019). Cannabidiol Enhances the Therapeutic Effects of TRAIL by Upregulating DR5 in Colorectal Cancer. Cancers, 11(5), 642. doi:10.3390/cancers11050642
  22. Kim, S. H., Yang, J. W., Kim, K. H., Kim, J. U., & Yook, T. H. (2019). A Review on Studies of Marijuana for Alzheimer’s Disease – Focusing on CBD, THC. Journal of pharmacopuncture, 22(4), 225–230.
  23. Elms, L., Shannon, S., Hughes, S., & Lewis, N. (2019). Cannabidiol in the Treatment of Post-Traumatic Stress Disorder: A Case Series. Journal of alternative and complementary medicine (New York, N.Y.), 25(4), 392–397.
  24. 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.
  25. World Health Organization (WHO). (2018). Cannabidiol (CBD) Critical Review Report.
  26. Machado Bergamaschi, M., Helena Costa Queiroz, R., Waldo Zuardi, A., & Crippa, A. S. (2011). Safety and side effects of cannabidiol, a Cannabis sativa constituent. Current drug safety, 6(4), 237-249.
  27. Corroon, J., & Phillips, J. A. (2018). A Cross-Sectional Study of Cannabidiol Users. Cannabis and cannabinoid research, 3(1), 152–161.
  28. Synthetic cannabinoids: What are they? What are their effects? Centers for Disease Control and Prevention. Retrieved from
  29. About synthetic cannabinoids. Centers for Disease Control and Prevention. Retrieved from
  30. Alipour, A., Patel, P. B., Shabbir, Z., & Gabrielson, S. (2019). Review of the many faces of synthetic cannabinoid toxicities. The mental health clinician, 9(2), 93–99.
  31. Brown, J. D., & Winterstein, A. G. (2019). Potential Adverse Drug Events and Drug-Drug Interactions with Medical and Consumer Cannabidiol (CBD) Use. Journal of clinical medicine, 8(7), 989.
  32. Ibid
  33. Leino A., Emoto C., Fukuda T., Privitera M., Vinks A., Alloway R. Evidence of a Clinically Significant Drug-Drug Interaction between Cannabidiol and Tacrolimus: A Case Report Am J Transplant. 2017;17 (suppl 3). Retrieved from 
  34. Qian, Y., Gurley, B. J., & Markowitz, J. S. (2019). The Potential for Pharmacokinetic Interactions Between Cannabis Products and Conventional Medications. Journal of clinical psychopharmacology, 39(5), 462–471.
  35. ISPE. What is GMP? Retrieved from
  36. Hazekamp A: The Trouble with CBD Oil. Med Cannabis Cannabinoids 2018;1:65-72. doi: 10.1159/000489287
  37. Karger Publishers. Karger. Retrieved from 
  38. Hazekamp A. Op cit
  39. Ibid
  40. Leweke FM, Piomelli D, Pahlisch F, et al. Cannabidiol enhances anandamide signaling and alleviates psychotic symptoms of schizophrenia. Transl Psychiatry. 2012;2(3):e94. Published 2012 Mar 20. doi:10.1038/tp.2012.15.
  41. Silver R. J. (2019). The Endocannabinoid System of Animals. Animals : an open access journal from MDPI, 9(9), 686.
  42. Sallaberry, C. and Astern, L. The Endocannabinoid System, Our Universal Regulator. Retrieved from
  43. Millar, S. A., Maguire, R. F., Yates, A. S., & O’Sullivan, S. E. (2020). Towards better delivery of cannabidiol (CBD). Pharmaceuticals, 13(9), 219.
  44. Price G, Patel DA. Drug Bioavailability. [Updated 2020 May 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from:
  45. Peace, M. R., Butler, K. E., Wolf, C. E., Poklis, J. L., & Poklis, A. (2016). Evaluation of Two Commercially Available Cannabidiol Formulations for Use in Electronic Cigarettes. Frontiers in pharmacology, 7, 279.
  46. Shmerling, R. Can vaping damage your lungs? What we do (and don’t) know. Harvard Health Publishing – Harvard Medical School. 2019 September 4. Retrieved from 
  47. Hu, D., Cullen, B., Tang, M., & Fang Y. (2020). The Effectiveness of Topical Cannabidiol Oil in Symptomatic Relief of Peripheral Neuropathy of the Lower Extremities. Current Pharmaceutical Biotechnology, 390-402.
  48. Farm Bill. U.S. Department of Agriculture. Retrieved from:
CBD Clinicals is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Learn more