Categories
BLOG

light sensitivity after smoking 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.

Cannabis may enhance night vision

Marijuana plants at the Ganja Farms marijuana store in Bogota, Colombia. Photo: Colombia-Cannabis/ Reuters/ John Vizcaino

Marijuana plants at the Ganja Farms marijuana store in Bogota, Colombia. Photo: Colombia-Cannabis/ Reuters/ John Vizcaino

New research shows that the drug makes cells in the retina more sensitive to light

Last modified on Tue 9 May 2017 18.30 BST

25 years ago, pharmacologist M. E. West of the University of the West Indies in Kingston, Jamaica, noted that local fisherman who smoke cannabis or drink rum made with the leaves and stems of the plant had “an uncanny ability to see in the dark,” which enabled them to navigate their boats through coral reefs. “It was impossible to believe that anyone could navigate a boat without compass and without light in such treacherous surroundings,” he wrote after accompanying the crew of a fishing boat one dark night, “[but] I was then convinced that the man who had taken the rum extract of cannabis had far better night vision than I had, and that a subjective effect was not responsible.”

Some of these crew members told West that Moroccan fishermen and mountain dwellers experience a similar improvement after smoking hashish, and in 2002, another research team travelled to the Rif mountains in Morocco to investigate further. They gave a synthetic cannabinoid to one volunteer, and hashish to three more, then used a newly developed piece of kit to measure the sensitivity of their night vision before and after. Confirming West’s earlier report, they found that cannabis improved night vision in all three of their test subjects.

Now, another study provides hard evidence for the claim, revealing a cellular mechanism by which cannabis might improve night vision. The findings, published recently in the open access journal eLife, could eventually be applied to the treatment patients with degenerative eye diseases such as retinitis pigmentosa.

West had suggested that cannabis might improve vision by acting on the eye muscles to dilate the pupils, so that more light falls on the retina, but other experiments ruled this out by showing that marijuana constricts the pupils. It’s also possible that the drug can influence activity in the visual cortex at the back of the brain, but the CB1 receptor protein, which binds the psychoactive ingredient of cannabis, is found at far higher levels in the eye than in the visual cortex, suggesting that any effects the drug has on vision are likely due to its actions on retinal cells.

Lois Miraucourt of the Montreal Neurological Institute and his colleagues looked not to stoned fishermen, but to tadpoles of the African clawed toad, Xenopus laevis, which are transparent and, therefore, amenable to all sorts of experiments that cannot be performed in humans or other lab animals.

In one set of experiments, they applied a synthetic cannabinoid to eye tissue preparations from the tadpoles, and used microelectrodes to measure how retinal ganglion cells, whose fibres form the optic nerve, respond to light. The researchers found that this made the cells more sensitive, increasing the rate at which they fired to both bright and dim light stimuli. Closer investigation revealed that this occurred due to inhibition of a protein called NKCC1, via its actions on the CB1 receptor.

NKCC1 is a co-transporter protein that normally shuttles sodium, potassium, and chloride ions in and out of cells, and their concentrations determine the electrical properties of nerve cells. Overall, these experiments show that cannabinoids reduce the concentration of chloride ions inside the retinal ganglion cells, making them more excitable and more sensitive to light.

Miraucourt and his colleagues then carried out another set of experiments to determine if the cellular responses they observed could contribute to vision. Tadpoles have a natural tendency to avoid dark moving dots, and the researchers exploited this by putting some tadpoles into a Petri dish, showing them dark dots under various lighting conditions, while using specially designed video-tracking software to track the movements of the tadpoles and the dots, and to measure the tadpoles’ avoidance responses.

Under normal lighting conditions, they observed no differences between tadpoles treated with a synthetic cannabinoid and untreated ones. In the dark, however, tadpoles given the cannabinoid avoided significantly more dots than untreated ones, which only responded to the dots as if by chance. Thus, the researchers conclude that the enhanced cellular responses observed in their first set of experiments improved the tadpoles’ sensitivity to contrast under low-light conditions.

Whether the findings are applicable to humans remains to be seen but, if so, they could pave the way to treatments for diseases such as retinitis pigmentosa and glaucoma, which cause blindness by killing off cells in the retina. Cannabinoids are known to have a neuroprotective effect on retinal cells, so treatments based on the drug may, in theory, not only improve vision for patients with deteriorating eyesight, but also slow down the progression of such diseases.

References

Miraucourt, L. S., et al. (2016). Endocannabinoid signaling enhances visual responses through modulation of intracellular chloride levels in retinal ganglion cells. eLife, 5: e15932. DOI: 10.7554/eLife.15932 [Full text]

Russo, E. B., et al. (2004). Cannabis improves night vision: a case study of dark adaptometry and scotopic sensitivity in kif smokers of the Rif mountains of northern Morocco. J. Ethnopharmacol., 93: 99–104 [PDF]

New research shows that the drug makes cells in the retina more sensitive to light ]]>