What’s the difference between CBD and THC?

In states where recreational and medicinal marijuana is legal, CBD and THC are becoming more and more popular. But, what are their effects exactly?

Alonso Martínez
Muscle & Joint Relief Cream with CBD at a cannabis trade show in New Tork (New York), in 2019.
Muscle & Joint Relief Cream with CBD at a cannabis trade show in New Tork (New York), in 2019.Mark Lennihan (AP)

With the legalization of cannabis distribution in several U.S. states over the past decade, the popularity of both CBD and THC products has soared. In 2020, up to one-third of American adults reported using CBD products, which have been marketed as treatments for various health conditions in recent years. However, many of these claims lack supporting evidence. Furthermore, THC-contaminated products may be falsely labeled as CBD, potentially leading to unintended drug interactions, inaccurate medical test results, or jeopardizing a user’s current or prospective employment.

According to the Substance Abuse and Mental Health Services Administration, “Cannabidiol (CBD) and Delta-9-tetrahydrocannabinol (delta-9 THC) are two of many chemical compounds called cannabinoids found in the cannabis plant.” Both CBD and THC bind to receptors in the brain and body but produce different effects. While THC disrupts “many mental and physical functions and produces psychoactive effects,” CBD does not.


In its pure form, the cannabinoid CBD does not produce any psychoactive effects and is typically derived from the hemp plant. CBD can lead to changes in alertness, mood (such as irritability and agitation), drowsiness, and/or sedation. Drug interactions with medications may result in side effects, and it could also affect the digestive system, causing symptoms like nausea or diarrhea. Long-term use may be associated with liver injury and potential male reproductive toxicity.

Several factors can influence the likelihood of experiencing adverse events or side effects associated with CBD usage. These factors include the product’s strength and purity, the quantity consumed, the method of administration, concurrent use or misuse of substances (both legal and illegal, including alcohol), and potential interactions with prescribed medications or other drugs.

Dried hemp plants are sorted and trimmed at Hepworth Farms in Milton, N.Y.,
Dried hemp plants are sorted and trimmed in Milton (New York), in 2021.Seth Wenig (AP)

In the United States, only one FDA-approved CBD product, Epidiolex, is available. Epidiolex is a pharmaceutical-grade CBD oral liquid used to treat severe forms of seizure disorders, although its exact mechanism of action is not fully understood. It can only be obtained in pharmacies with a valid prescription from a healthcare provider. Other over-the-counter CBD products are marketed for various health conditions despite limited evidence supporting their effectiveness or safety.

Non-FDA-approved CBD products are widely popular and come in various forms, including lotions, oils, creams, food and beverage items, tea, cosmetics, and even products for pets. These products may contain more than 0.3 percent THC and are not regulated by the FDA, potentially carrying biological and chemical contaminants due to unsafe manufacturing practices without adequate process controls. CBD products purchased from dispensaries may be subject to some form of oversight and standardization, but research suggests that labeled concentrations of CBD products are unreliable.


Delta-9-THC is a psychoactive cannabinoid found in trace amounts in cannabis plants and is typically synthesized from CBD using chemicals. According to SAMHSA, the manufacturing process may introduce harmful chemicals and biological contaminants.

A man smokes a liquid containing THC from an e-cigarette, in August 2019.
A man smokes a liquid containing THC from an e-cigarette, in August 2019.Robert F. Bukaty (AP)

Short-term effects of THC include altered senses, distorted perception of time, changes in mood, delusions, difficulty thinking, impaired movement, impaired memory, hallucinations, and psychosis. THC can have long-term effects on the brain and nervous system, such as impaired brain development, learning, memory, and thinking, and potential impacts on child development if used during pregnancy. It may also increase the risk of developing mental illnesses like depression or anxiety, in addition to causing respiratory and digestive problems.

Cannabis expert Dr. Mafer Arboleda explains that THC can induce a “feeling of well-being and pleasure” when used recreationally. In lower doses, it may help alleviate chronic pain, induce sleep, and improve appetite in certain medical conditions. In some jurisdictions, medical cannabis programs permit the use of THC-containing products for specific medical conditions.

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