To make matters more confusing, nine states (including California, Washington, and Colorado) let residents buy cannabis-based products with or without THC. Nearly two dozen other “medical marijuana states” allow the sale of cannabis, including capsules, tinctures, and other items containing CBD or THC, at licensed dispensaries to people whose doctors have certified that they have an approved condition (the list varies by state but includes chronic pain, PTSD, cancer, autism, Crohn’s disease, and multiple sclerosis). Sixteen more states legalized CBD for certain diseases.
The list of cannabinoids currently comprises 113 entries, with more and more additions each year. Of these 113, by far the best documented are tetrahydrocannabinol and cannabidiol (in this order), with the two also being the most abundant constituents of the cannabis plant. In a typical chemical isolation process, cannabidiol makes up a little under half of the entire extract.
CBD has been touted for a wide variety of health issues, but the strongest scientific evidence is for its effectiveness in treating some of the cruelest childhood epilepsy syndromes, such as Dravet syndrome and Lennox-Gastaut syndrome (LGS), which typically don’t respond to antiseizure medications. In numerous studies, CBD was able to reduce the number of seizures, and in some cases it was able to stop them altogether. Videos of the effects of CBD on these children and their seizures are readily available on the Internet for viewing, and they are quite striking. Recently the FDA approved the first ever cannabis-derived medicine for these conditions, Epidiolex, which contains CBD.
Our bodies are thought to produce endocannabinoids by the billions every day. “We always thought the ‘runner’s high’ was due to the release of dopamine and endorphins. But now we know the euphoria is also from an endocannabinoid called anandamide,” its name derived from the Sanskrit word for bliss, says Joseph Maroon, MD, clinical professor and vice chairman of neurosurgery at the University of Pittsburgh Medical Center. We produce these natural chemicals all day, but they fade quickly because enzymes pop up to destroy them. That’s where CBD comes in: By blocking these enzymes, CBD allows the beneficial compounds to linger.
It’s thought that the endocannabinoid system may be critical for regulating sleep and sleep stability, which make sense, as it promotes balance throughout the body. Research seems to show that when CBD interacts with this system, sufferers may achieve longer periods of overall sleep. Furthermore, earlier research demonstrated that CBD may provide relief for insomnia sufferers who struggle to achieve REM sleep due to anxiety. (33, 34, 35)
Although CBD oils aren’t regulated by the FDA, purchasing products stateside from one of the nine states where recreational and medical cannabis use is legal will likely result in a higher-quality product than buying one made with hemp-derived CBD oil imported from abroad, says Martin Lee, director of Project CBD, a nonprofit that promotes medical research into CBD.
Then there is the matter of which part of the plant is used. THC tends to be more concentrated in the leaves of the plant, while CBD in its stem and seeds. It should be noted that these aspects are relative. Some degree of agreement exists that for the purest CBD, the stalk of a hemp plant (varieties of cannabis generally grown for fiber manufacturing, low in THC), or much less often the seeds. Taking into account the fact that CBD supplements are usually in an oil form, one may fathom the origins of the nearly ubiquitous hemp oil dietary supplements. 
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