Q: What is the difference between THC and CBD

The difference between THC and CBD is important to know, especially in home care as patients oftentimes purchase these products without understanding what they are getting or how the products work. Both delta-9-tetrahydrocannabinol (THC) and cannabinol (CBD) are derived from the cannabis plants: Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These plants contain a highly variable blend of approximately 400 chemical compounds of which approximately 80 are naturally occurring cannabinoids.

THC is the most abundant cannabinoid in the cannabis plant and produces the euphoric, psychoactive effect that influences mood, consciousness, and behavior. THC is also neurotoxic, causing cognitive dysfunction, particularly learning, memory, attention and working memory (Mammen et al., 2018). Moreover, it increases appetite, and is sedating. Marijuana contains substantial amounts of THC which is primarily responsible for the effects of marijuana on a person's mental state. Side effects of THC are dose-dependent, including hypotension, hallucinations, tachycardia, central nervous system depression, euphoria, dizziness, drowsiness, somnolence, confusion, new or worsening nausea/vomiting, and seizures. People can overdose on THC when using edibles as it is difficult to determine exact dosing (this is less likely if smoking or vaping). Symptoms of overdose range from mild to severe. Milder overdoses are characterized by nausea, anxiety, lethargy, dizziness, and paranoia. Severe overdoses include cannabinoid hyperemesis syndrome and marijuana-induced psychosis. The former involves bouts of severe vomiting and abdominal pain-usually lasting for less than 24 hours (https://www.webmd.com/connect-to-care/addiction-treatment-recovery/marijuana/sym).

CBD is the second-most studied cannabinoid. Although both THC and CBD are psychoactive agents, THC's psychoactivity is more likely to cause impairment than CBD. Studies have shown that CBD can improve mood by decreasing anxiety and depression as well as other nonpsychiatric conditions (e.g., nausea/vomiting, seizures, inflammatory, neurodegenerative disorders, and pain). CBD side effects are also dose-dependent, and include dizziness, anxiety, diarrhea, jitteriness, decreased appetite, hepatocellular injury, sedation, and suicidal ideations.

Hemp is defined as any part of the Cannabis sativa plant. To be classified as hemp, it cannot contain more than 0.3% THC on a dry weight basis (https://www.fda.gov/news-events/congressiol-testimony/hemp-production-and-2018-f). Most hemp is cultivated for nonpharmacologic use such as paper, clothing, cosmetics, cordage (twine, string, yarn, cable), food, and burlap. Because of the low percent of THC, hemp is not used to get high.

The FDA has approved three synthetic THC formulations and one plant-derived CBD medication for medical use. The three synthetic THC formulations include Marinol (Schedule III, approved May 31, 1985), Syndros (Schedule II, approved July 1, 2016), and Cesamet (Schedule II, approved May 15, 2006). Marinol and Syndros are approved for the treatment of anorexia in AIDS and nausea/vomiting with chemotherapy unresponsive to conventional antiemetics, and Cesamet is approved for chemotherapy-related nausea/vomiting. Epidiolex, a CBD oil, has been approved (Schedule V, approved June 25, 2018) for seizures associated with Dravet syndrome and Lennox-Gastaut syndrome in children 1 year and older. These approved drugs products are only available with a prescription from a licensed healthcare provider (https://www.fda.gov/news-events/public-health-focus/fda-and-cannabis-research-an).

Cannabis has been classified as a Schedule I drug, the most restrictive category, since 1971 making it illegal to use or possess under federal law in the United States (Controlled Substance Act, Title 21, Section 811; https://www.dea.gov/controlled-substance-act). However, 36 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands have approved cannabis for medical purposes. Additionally, another 18 states and the District of Columbia have approved cannabis for recreational use (https://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx).

Retraining the brain to treat chronic pain

NIH: More than 25 million people in the U.S. live with chronic pain (lasting more than 3 months). Despite costing more than $600 billion a year, existing treatments for chronic pain fail to provide relief for many people. The most common type of chronic pain is chronic back pain. In about 85% of cases, no physical cause can be found. Such unexplained pain is thought to be caused by brain changes after an injury that persist even after the damage heals. Researchers developed a treatment called pain reprocessing therapy (PRT) to help the brain "unlearn" this pain, teaching people to perceive pain signals sent to the brain as less threatening. Therapists help participants do painful movements while helping them re-evaluate the sensations they experience. In the study, 151 people with mild to moderate back pain for which no physical cause could be found received one of three treatments: four weeks of intensive PRT, a placebo injection of saline into the back, or a continuation of care as usual. Participants rated their pain before and four weeks after starting treatment. They also underwent MRI scans to look at brain activity before and after treatment. After 4 weeks of PRT, 66% of people who underwent the therapy reported being pain-free or nearly pain-free. In contrast, only 20% of people who received placebo injections and 10% of those receiving usual care reported similar improvements. The reductions in pain after PRT were largely maintained a year after treatment.

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