字幕列表 影片播放 列印英文字幕 Cannabis is receiving more and more attention from doctors, research groups, and the public as a possible treatment for lots of different medical conditions. But it's also met with lots of hesitation, because marijuana has psychoactive properties and we still have a pretty limited understanding of its effects. Lately, though, some scientists have been studying a compound in cannabis that might have medical benefits without causing a high. It's called cannabidiol. The most famous ingredient in weed is the one that gets you high: THC, or delta-9 tetrahydrocannabinol. THC is a kind of cannabinoid – a molecule that binds to cannabinoid receptors on your cells. Normally, these receptors are activated by chemicals made by your body called endocannabinoids. There are two main kinds of cannabinoid receptors, and they're expressed in different parts of your body. CB1 is mostly in your brain, and CB2 is in your immune system and in your peripheral nervous system – basically, any nerves that aren't in your brain or spinal cord. So cannabinoid signaling affects a lot of different systems in your brain and body, and, for a long time, research involving cannabis has only focused on THC. But marijuana has over 60 different kinds of cannabinoids, and we're realizing some others are really interesting too – like cannabidiol, or CBD. CBD is also a major component of pot. It's kind of like THC's responsible older brother. In fact, it's got the same chemical formula, but the atoms are arranged in a slightly different way. The different structure means that CBD can't bind to cannabinoid receptors the way that THC can, and scientists think that's why CBD doesn't have psychoactive properties. It even seems to be an antagonist, or blocker, of chemicals that bind to cannabinoid receptors. Plus, CBD might bind to other kinds of receptors – like GPR55, which lets calcium into cells, and a bunch of TRP receptors, that sense temperature and pain. Beyond these guesses, we're still not really sure how CBD can affect your brain and body. But there's a lot of appeal in a cannabinoid-based medication that doesn't get you high. So in the last decade or so, research on CBD has exploded. For example, cannabis has been used as a treatment for epilepsy seizures for a really long time. And we're still not sure exactly how it works, because there hasn't been much solid research. But CBD is an appealing treatment option, since the lack of a high means it could be used on a regular basis. A recent study looked at whether CBD might be a safe and effective medication for treatment-resistant epilepsy in people ages 1 to 30. Of the 162 patients in the safety portion of the study, some had to drop out because of adverse events like stomach issues or excessive sleepiness, but not all of these symptoms were necessarily because of the CBD. In total, 137 patients were examined for how effective CBD was at treating seizures. It seemed to help reduce seizures by an average of about 35%, and a few patients didn't have any seizures during the trial. So it does seem to help with severe epilepsy. But, this was a pretty small study. And it's what's known as an open label study, so there was no control group. So we definitely need to better understand the side effects and risks before it becomes a standard treatment. CBD also seems to have some anti-inflammatory properties. Research on mice brains has found that CBD might lower the levels of inflammatory proteins called cytokines. These proteins play roles in all kinds of conditions in humans, like Alzheimer's Disease and migraines. And studies on isolated neurons also suggest that CBD is an antioxidant, so it could help protect cells from degeneration caused by conditions like Alzheimer's. These properties haven't been studied in living humans yet, though, so it's too soon to say if the same is true in actual brains. Marijuana has been prescribed for chronic pain treatment for a while, but it's only recently been studied in any sort of depth. Several different reviews of clinical trials have found that patients prescribed treatments containing THC and CBD reported pain relief compared to a placebo, but it's not a huge effect. It's not totally clear how cannabis relieves pain, but the link between CBD and the TRP channels, which play a major role in pain sensation, means that CBD could play a big part. Lastly, CBD seems to have anti-nausea properties, too. Some scientists have found evidence that giving rats CBD can suppress vomiting, by activating serotonin receptors in areas of the brain associated with nausea. Because of this, it might be able to help cancer patients undergoing chemotherapy. Overall, though, there are a lot of unknowns when it comes to CBD as a safe, effective medical treatment. We don't fully understand a lot of things, like: what's different about how it binds to cannabinoid receptors, why it doesn't cause a high, and what kinds of effects it has on the body and brain during long-term treatment. Another strong medication that can treat serious conditions – especially things like chronic pain – that doesn't have psychoactive properties would be an amazing new tool in medicine. That way, patients can have an option besides things that can be tremendously habit forming, like opioids. Or, just mess you up for a little bit, like THC. But we still have a lot to learn before we know for sure if CBD is a good alternative. Thank you for watching this episode of SciShow, which was brought to you by our patrons on Patreon. 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