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do your eyes dilate when you smoke weed

An Expert Explains What Happens To Your Body When You Smoke Weed

It’s not just bloodshot eyes and munchies.

Whether you’re an avid stoner or never touched a joint in your life, chances are you’re familiar with the things that happen when you smoke weed. 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.

You probably 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).

“The effects of marijuana depend in part on the strain of marijuana and whether the person is a chronic user or not,” Dr. Keith Heinzerling M.D., addiction medicine specialist at Providence Saint John’s Health Center, tells Bustle. A giant hit of a high-THC strain will affect you very differently than if you have a tiny nibble on a pot cookie.

But what causes the red eyes? Why do some people experience cotton mouth or find it affects their sex life? 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.

1. Dopamine Floods Your Brain

Like most drugs, cannabis’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 “pleasure, memory, thinking, concentration, movement, coordination, and sensory and time perception.”

“THC acts through cannabinoid receptors in the brain and body,” Heinzerling says. Using these 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 cannabis. Heinzerling adds that dopamine isn’t the only thing that’s affected by weed; it also alters other receptors for neurotransmitters like GABA and serotonin, which influence your mood. Your particular flavor of high depends on which neurotransmitters are impacted.

2. Body Fluids Dry Up

Talk about a mood killer. A study published in Journal Of Sexual Medicine in 2010 found 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 cannabis 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 cannabis. 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 your 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. This is the reason that THC affects your cognition and coordination when you’re very high, Keinzrling says – and it’s why driving while stoned is a bad idea.

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. Heinzerling says THC can also heighten your risk of anxiety and panic attacks, which make the heart pound rapidly. Although a quick heart rate is often harmless, the National Institute on Drug Abuse notes that a racing heart rate 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 cannabis increases appetite, and recently, science has begun to shed light on the reason. “THC is responsible for most of the psychoactive effects associated with cannabis use including the high as well as increased appetite (“munchies”),” Heinzerling says. According to a 2015 study published in Nature Neuroscience, 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.

Readers should note that laws governing cannabis, hemp and CBD are evolving, as is information about the efficacy and safety of those substances. As such, the information contained in this post should not be construed as legal or medical advice. Always consult your physician prior to trying any substance or supplement.

Keith Heinzerling M.D.

Crean, R. D., Crane, N. A., & Mason, B. J. (2011). An evidence based review of acute and long-term effects of cannabis use on executive cognitive functions. Journal of addiction medicine, 5(1), 1–8. https://doi.org/10.1097/ADM.0b013e31820c23fa

Koch, M., Varela, L., Kim, J. et al. (2015) Hypothalamic POMC neurons promote cannabinoid-induced feeding. Nature519, 45–50. https://doi.org/10.1038/nature14260

Prashad, S., & Filbey, F. M. (2017). Cognitive motor deficits in cannabis users. Current opinion in behavioral sciences, 13, 1–7. https://doi.org/10.1016/j.cobeha.2016.07.001

Smith, A. M., Ferris, J. A., Simpson, J. M., Shelley, J., Pitts, M. K., & Richters, J. (2010). Cannabis use and sexual health. The journal of sexual medicine, 7(2 Pt 1), 787–793. https://doi.org/10.1111/j.1743-6109.2009.01453.x

Winton-Brown, T. T., Allen, P., Bhattacharyya, S., Borgwardt, S. J., Fusar-Poli, P., Crippa, J. A., Seal, M. L., Martin-Santos, R., Ffytche, D., Zuardi, A. W., Atakan, Z., & McGuire, P. K. (2011). Modulation of auditory and visual processing by delta-9-tetrahydrocannabinol and cannabidiol: an FMRI study. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 36(7), 1340–1348. https://doi.org/10.1038/npp.2011.17

This article was originally published on Feb. 11, 2016

Whether you’re an avid stoner or never touched cannabis in your life, chances are you’re familiar with the things that happen when you smoke weed.

Why does weed make your eyes red?

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Contents

  1. Under pressure: lower blood pressure and dilated capillaries
  2. Do edibles make your eyes red?
  3. The redder the better?

Among the most common effects of marijuana use (and telltale signs you’ve recently partaken) is red, bloodshot eyes. It’s to be expected, sure, but that doesn’t answer the mysterious question pondered by generations of stoners: why does weed make your eyes red?

For weed novices, the onset of bloodshot eyes could cause a panic-induced internet search asking “ can smoking weed damage your eyes? ” Thankfully, as those who regularly consume cannabis can tell new users, there are no serious health risks associated with your sudden red-eyed circumstance. You’re probably not experiencing an allergic reaction or some bigger complication. Some might poke fun or chastise you for sporting your so-called “ weed eyes ” in public, but otherwise, it’s a completely natural occurrence that transpires after smoking cannabis.

In fact, your eyes turning red has nothing to do with the act of smoking at all.

Under pressure: lower blood pressure and dilated capillaries

After consuming a cannabis-based product (flower, concentrate, edible, etc.), users generally experience an increase in heart rate and blood pressure. This effect is due to the plant’s cannabinoids, which are chemical compounds responsible for some of the therapeutic and medicinal benefits of cannabis, and their initial interaction with the body. This rise in blood pressure and heart rate is comparable to normal physical activities like exercise or sex.

It generally takes about five to ten minutes for users’ heart rates to return to normal and for blood pressure to begin to decrease. As the blood pressure lowers, the blood vessels and capillaries dilate, including the ocular capillaries . The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red and also reduces intraocular pressure.

The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red in the process, and also reduces intraocular pressure. Photo by: Gina Coleman/Weedmaps

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In fact, according to Dr. Melanie Bone, a board-certified OB-GYN who practices in West Palm Beach, Florida, “It’s cannabis’ ability to reduce intraocular pressure in the eyes that makes it a potentially viable treatment for glaucoma , a group of eye disorders that causes damage to the optic nerves which can eventually lead to blindness. It also happens to explain why your eyes become bloodshot after smoking cannabis.”

Evidence that the THC found in cannabis can lower intraocular pressure (IOP) is a major reason why many glaucoma patients have attempted to use medical marijuana to treat and relieve symptoms of the disease. It’s important to know that some studies have contradicted or added a caveat to the claim that cannabis is beneficial for glaucoma. For instance, a 2018 study conducted at Indiana University found that cannabidiol (CBD), the non-intoxicating cannabinoid found in marijuana, could potentially worsen the condition by increasing eye pressure . More research into the use of cannabis for glaucoma treatment is needed.

Do edibles make your eyes red?

Similar to smoking cannabis, ingesting edibles could also make your eyes turn red. Again, this depends on the amount of THC consumed. Remember, it’s not the smoke itself that makes your eyes red, but rather the ability that cannabinoids have to lower blood pressure, causing blood vessels and capillaries to dilate.

The redder the better?

The amount your blood pressure is lowered and how red your eyes become depends on the amount of THC you consume.

Tetrahydrocannabinol (THC), the most common cannabinoid in the plant, is responsible for the intoxication associated with smoking cannabis. The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.

The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.

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So, red eyes can act as a sign that your cannabis has a high cannabinoid content (i.e., it’s potent). In other words, if your eyes are noticeably bloodshot after consumption, there’s a good chance you’ve landed yourself some highly potent weed.

Other than being a dead giveaway that you’ve recently consumed cannabis, you have no reason to be concerned about the redness of your eyes. Cannabis-induced eye redness will typically only last a few hours and can easily resolve if you have the right tools at your disposal.

It isn’t a bad idea to have eye drops (or some sunglasses) on hand. Look for eye drop brands that are specifically designed to reduce eye redness. There are other methods that could potentially help combat cannabis-induced bloodshot eyes, including staying hydrated, washing your face and eyelids with cold water, or simply consuming cannabis products with lower THC levels.

Ever wonder why using marijuana or cannabis makes your eyes red or bloodshot? Discover why weed gives you bloodshot eyes.