Herbalists say that for every poisonous plant, there’s another with an antidote not far away. That kind of balance between opposites is everywhere in nature—and that may help to explain the interplay between THC and CBD, the two most plentiful compounds in the marijuana plant. Although these two substances appear to have opposing effects, in combination each affects the action of the other to keep the marijuana high from spinning out of control—and create some potent healing benefits.
THC (officially known as delta-9-tetrahydrocannabinol) is the most prevalent of more than one hundred compounds found in the marijuana plant. It’s followed closely by cannabidiol, or CBD. Separately and together, these two compounds are the cannabis ingredients to be most closely studied for their applications in treating a wide range of health conditions ranging from cancer to PTSD.
THC is probably the best known of marijuana’s many compounds. Its psychoactive properties are responsible for the cannabis “high” enjoyed by recreational users—and for keeping marijuana on the DEA’s list of what they consider to be highly addictive and dangerous drugs.
For most users, that high delivers a feeling of relaxation and euphoria. But for others, THC can cause less pleasant reactions—nervousness, anxiety and paranoia. The likelihood of those kinds of negative effects rises when a user consumes cannabis grown from strains that are very high in THC. Some studies also suggest that long term or extensive use of THC can permanently affect brain functions such as memory or cognition.
But THC isn’t just good for a good time as it also has potent healing properties. The endocannabinoid system is a vast network of natural cannabinoid receptors that occur throughout the body. These receptors can be filled by cannabinoids manufactured by the body itself, or by introducing cannabis from outside sources like smoking or consuming it.
The body’s CB1 and CB2 receptors are abundant in the brain, organs and tissues, and THC binds with them in ways that are nearly identical to natural endocannabinoids such as anandamide and 2-AG. That means THC can be beneficial in treating a wide range of health conditions affecting both body and mind—especially when it’s accompanied by CBD.
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CBD is the second most common compound found in cannabis, and although it lacks the psychoactive properties of THC, many studies have found that it has numerous whole body health benefits, such as reducing inflammation and boosting immune system functions. Available in forms such as oil concentrates, edibles and even skin creams and ointments, CBD can help reduce chronic pain, ease the symptoms of autoimmune disorders and migraines, and reduce the nausea associated with cancer treatment.
But while THC binds directly with the body’s own endocannabinoid receptors in the brain, central nervous system and other organs and tissues, CBD works in more mysterious ways. Whether it’s the raw plant form known as CBDA or the extracted version CBD, this compound doesn’t directly bind with either of the body’s cannabinoid receptors. Rather, it either enhances or inhibits the activity of a long list of other receptors and channels that affect processes ranging from the proliferation of cells (particularly cancer cells) to the uptake of the calming neurotransmitter GABA.
CBD also has the ability to act allosterically on some kinds of receptors. That is, it can change the receptor’s shape to affect its behavior, either positively or negatively. And in that capacity, CBD can affect the endocannabinoid receptor CB1, even though it doesn’t bind directly to it. As a negative allosteric modulator, CBD weakens the ability of CB1 receptors to bind to THC, and that limits the psychoactive effects of THC while preserving its therapeutic qualities.
The “entourage effect” is what happens when multiple elements work together to enhance the positive effects of them all. When THC and CBD are used in combination, they produce much greater benefits than when used alone. And studies reveal that those benefits in turn are amplified when the whole marijuana plant is used, rather than isolated extracts of THC and CBD. The combination of THC’s direct effects on the endocannabinoid system and CBD’s activity on other kinds of receptors accounts for the most potent healing properties of cannabis.
CBD helps to prolong the effects of THC therapies for cancer and other conditions. Because CBD is able to weaken CB1’s ability to bind with THC, it slows the breakdown of THC in the liver, so that the effects of the treatment last longer. Studies also reveal that the combination of THC and CBD is more able to enhance the effectiveness of radiation therapy to treat high-grade glioma—an aggressive and usually inoperative cancer of the brain—than either of these compounds alone.
Research also suggests that THC may be helpful in reducing the anxiety and hyperarousal common in Post Traumatic Stress Disorder (PTSD), precisely because that psychoactive high produces feelings of relaxation and can also help eliminate negative memories. But THC is more effective when combined with CBD, which keeps THC’s psychoactivity under control, so that its negative psychoactive effects don’t undermine treatment.
THC and CBD alone both have their own medicinal benefits. But in combination, the whole seems to be greater than the sum of its parts. The exact proportions of THC relative to CBD in a particular treatment can vary widely, depending on the individual and the goals of the treatment, but finding a balance between these two compounds may be the key to unlocking the many healing benefits of cannabis.