Weed is famous for its ability to relieve nausea, but it can have the opposite effect in people who smoke a lot of it. The little-known condition, called cannabinoid hyperemesis syndrome (CHS), involves bouts of extreme nausea, vomiting, and stomach pain, and can be temporarily relieved by a hot shower.
The condition has only been known to scientists for a few years, and it's still rare. But it's also hard to diagnose: many doctors don't know about it, and many cannabis users find it hard to believe that something they have been using for years could suddenly cause problems.
A recent study found that CHS may be more common than we realised. Researchers gave a questionnaire to people who were at a New York City emergency room for other reasons, and not currently experiencing nausea. (Many medical conditions can cause nausea, so they wanted to rule out the possibility that people were suffering from something else. If you have CHS, it tends to come and go.)
Of 155 patients who filled out the survey and who used cannabis at least 20 days per month, 33 per cent said that they find hot showers to be an effective way to relieve nausea. If those numbers turn out to be representative of cannabis users in general, that means a few million people in the US might experience CHS, and probably most of them have no idea.
We don't know exactly what causes CHS, or why hot showers help. Our digestive system contains receptors for endocannabinoids, our body's natural chemicals that cannabis mimics. Meanwhile, a region of the brain that controls body temperature, the hypothalamus, also has cannabinoid receptors — so there may be a connection between that brain area and the hot shower relief.
If you think you have CHS, get checked out — your nausea may end up being caused by something else. But if it really is the cannabis that's at fault, the only known cure is to stop using it. You can read more about cannabinoid hyperemesis syndrome here.