If you're looking for a short answer, the main difference between CBD and THC is in the molecular structure that allows THC to bind to CB1 receptors in the human body's endocannabinoid system that result in the "high" feeling experienced when inhaling or ingesting cannabis. CBD has a slightly different molecular structure to where it cannot bind with CB1 receptors and therefore does not cause the high feeling experienced with THC.
Although CBD does not get users high, it has been shown to provide anti-inflammatory and anti-anxiety benefits for users. CBD, when present with THC, can actually reduce the severity of the high experienced when ingesting or inhaling THC. While CBD does not bind with CB1 receptors, it can block THC from binding with some CB1 receptors therefore reducing the psychoactive effects of the THC.

For a more complete answer on the similarities and differences between THC and CBD, read on.

Understanding Phytocannabinoids and the Endocannabinoid System

THC and CBD are phytocannabinoids; these are chemical compounds produced in a cannabis plant (or hemp plant) as it grows and matures. These chemical compounds are absorbed by the human body and interact with the body’s endocannabinoid system when inhaled or ingested. The endocannabinoid system exists throughout the human body and is responsible for keeping our physiological, emotional, and cognitive abilities stable. The endocannabinoid system is made up of CB1 and CB2 receptors that are responsible for keeping the body in a stable state. Our body produces natural cannabinoids that interact and bind to CB1 and CB2 receptors to keep our body in homeostasis. THC and CBD, or phytocannabinoids, mimic these cannabinoids produced by our body that can influence hunger, motivation, pleasure, healing, among other responses.

The slight difference in molecular structure between CBD and THC is what allows THC to bind to CB1 receptors that results in a high feeling that we don't get from CBD. THC's molecular structure contains a cyclic ring while CBD has a hydroxyl group and this minor difference is what prevents CBD from being able to bind directly with CB1 receptors in our body. THC however, has the same molecular structure as the neurotransmitter Anandamide, which is a natural cannabinoid created in the body that is typically produced after some form of exercise resulting in what some people call a "runner's high". Anandamide helps regulate inflammation and assists in the generation of hunger, pleasure and motivation. By having the same molecular structure as Anandamide, THC is able to bind directly to CB1 receptors that transmit messages to the body that help with pain relief, nausea, insomnia, and appetite stimulation. Although CBD doesn't bind directly with the receptors in our endocannabinoid system, it activates other receptors throughout the body that offer many positive effects on the body. CBD has shown to activate a number of serotonin receptor that can alleviate symptoms like nausea, anxiety, and pain.

Can THC and CBD Work Together?

With so many different cannabis strains, there are a number of plants with varying levels of both THC and CBD. Many medical marijuana patients enjoy having the ability to consume cannabis with high levels of CBD and low levels of THC to keep their minds clear and calm while still enjoying the health benefits. While CBD may not bind directly to CB receptors in our endocannabinoid system, it can block THC from binding to receptors therefore reducing the high feeling created when THC binds to CB1 receptors. Cannabis with high levels of both THC and CBD may offer the most health benefits but if you are looking to experience the psycho active effects of cannabis, choosing a high THC strain with low to no CBD would be your best option.

Additional Information on THC and CBD

In 2018, the FDA approved the use of Epidiolex® to treat seizures associated with Lennox-Gastaut syndrome (LGS), Dravet syndrome, or tuberous sclerosis complex (TSC) in patients one year of age and older. Epidiolex® contains only CBD and has been used to reduce the severity and frequency of seizures. CBD was technically still a controlled substance when Epidiolex® was approved by the FDA but as of 2020 has been removed from the controlled substances list. In 2018 the federal government also legalized the production of hemp in order to be able to produce CBD legally across all of the United States. While some states still have laws restricting the production and sale of CBD it has become a trusted and effective way to treat patients suffering from conditions leading to seizures. The acceptance of CBD as a form of medical treatment is monumental in the ability to continue to research and learn the benefits of both CBD and THC. The endocannabinoid system itself wasn't discovered or defined until 1992 by the Israeli chemist, Raphael Mechoulam. Additional research and study of THC and CBD will likely lead to additional breakthroughs and discoveries on how these phytocannabinoids interact with the human body.