Whether you're an avid stoner or never touched marijuana in your life, chances are you're familiar with the things that happen when you smoke weed — or, rather, their effects. The drowsiness, the giggles, the sudden deep desire to discuss eighth grade philosophy, and other such overt symptoms are all the result of hidden processes going on in your body when you get high. Many have at least a vague understanding of how weed works: The chemical tetrahydrocannabinol, better known as THC, zips through your bloodstream after ingestion and interacts with parts of your brain like the hippocampus and orbitofrontal cortex to cause a high. It's more complicated than that, of course, but the general concept isn't difficult to grasp (unless you've had one too many pot brownies).
However, the layman's knowledge tends to stop there. Most people know the overt symptoms of toking up, but what causes the red eyes? Why do some people experience cotton mouth or "weed dick?" Perhaps most importantly, what's the deal with the munchies? Fortunately for the curious — or those who prefer to know what's going on inside their bodies — there's plenty of research devoted to answering these questions. Let's take a look at six things that happen to your body when you smoke weed below.
1. Dopamine Floods Your Brain
Like most drugs, marijuana's high comes from the neurotransmitter dopamine, which is associated with our brain's reward system; as noted by a study in the National Institute of Drug Abuse, dopamine is responsible for "influence pleasure, memory, thinking, concentration, movement, coordination, and sensory and time perception." Acting through cannabinoid receptors, THC stimulates the release of dopamine in large amounts, causing feelings of euphoria. It's this reaction that's responsible for the "high" you feel after using marijuana.
2. Body Fluids Dry Up — Including Your Vagina
Talk about a mood killer. Research has shown that weed can temporarily dry up mucus membranes throughout your body, including your vagina — hence the term "cotton vagina" that's been, well, cottoning on in some circles. Other mucus membranes in your body include your eyes and mouth, so you may feel dryness effects in those regions too, depending on the strain of marijuana and your individual reactions to them.
3. Your Blood Pressure Drops
Weed causes blood vessels across your body to dilate, creating a drop in blood pressure. This is most apparent in your eyes; as your blood vessels expand, they appear red, and your pupils may become dilated — this is what gives people the "bloodshot" look in their eyes after using marijuana. Simultaneously, breathing passages relax and open up, which contributes to the feeling of relaxation and calm that some people experience during a high.
4. Your Senses Get More Intense
You might notice that in addition to the depressive effects of a slower heart rate and the widening of your breathing passages, your senses also seem more acute — you may notice different smells, touches, or other sensations that you might not normally note, or experience them in more intense degrees. This is because, in addition to triggering the release of dopamine, THC binds to brain receptors associated with our senses of smell and taste, which has been shown to heighten their sensitivity. Combined with the side effect of pupil dilation, many of your senses can become temporarily heightened.
5. Your Heart Rate Increases
Despite the fact that weed is used for many as a relaxant, what you may not realize is that smoking weed is known to speed up your heart rate for up to three hours after getting high; the dilation of your blood vessels causes the muscles in your heart to work harder to pump blood. Although this is often harmless, the National Institute on Drug Abuse notes that it can increase your chances of having a heart attack, especially when combined with the drop in blood pressure.
6. Your Sense Of Hunger Is Distorted
Even if you don't smoke, you're no doubt familiar with the munchies. Researchers (and stoners) have long known that marijuana increases appetite, and recently, science has begun to shed light on the reason: According to a 2015 study, THC "flips a switch," so to speak, on the neurons that were previously responsible for telling your body to stop eating. When you get high, these neurons begin signaling that you're actually starving — and suddenly you find yourself in the Taco Bell parking lot surrounded by what used to be seven burritos.
This post was originally published on February 11, 2016. It was updated on June 6, 2019.