Cannabis sativa, more commonly known as marijuana, is a drug that has been legalized in various states for medicinal reasons and legalized in some states for recreational use as well. The drug has a long history of use and abuse in the United States.>

Even though some states have legalized it, the United States Drug Enforcement Administration (DEA) continues to classify cannabis products as Schedule I controlled substances, placing them in a class of drugs with supposedly no medical uses and with the potential for significant abuse. Nonetheless, numerous research studies indicate that cannabis products do have some medicinal uses, and certainly, the prevailing attitude by many has shifted to the notion that marijuana is no more harmful than legal substances like tobacco and alcohol. Whether or not marijuana is used for recreational purposes or for medicinal reasons, the use of the drug produces various side effects.

Increased Hunger

The experience of having the “munchies” after using cannabis products is widespread. Even though some people don’t have this experience, it appears that the vast majority of individuals who use cannabis products do report increased feelings of hunger at some time. The specific mechanism of how cannabis results in increased hunger in individuals is not fully recognized; however, some of what is known has been described in several recent research studies that have looked at the appetite-stimulating effects of cannabis products in people and in animal models, particularly in rodents.

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According to numerous sources, such as a much-cited research article published in the journal Nature Neuroscience, there are several possible mechanisms associated with an increase of hunger and marijuana use.

  • Cannabinoids, which are the active ingredients in marijuana, affect an individual’s brain in numerous ways. The most well-known of these is delta-9- tetrahydrocannabinol (THC), which is responsible for the psychoactive effects of marijuana (the “high” associated with cannabis). However, there are more than 80 recognized cannabinoids in marijuana products that all have different effects. The cannabinoids in marijuana are very similar in their structure to neurotransmitters that attach to receptor sites in the brain, known as endogenous cannabinoid receptor sites.
  • When there is a decrease in energy stores (fat cells and glucose levels in the blood) in the body, the gastrointestinal tract triggers the release of the hormone ghrelin. This hormone stimulates the hypothalamus to increase feelings of hunger, which also stimulates the ventral tegmental area of the brain and increases the release of dopamine. THC is known to stimulate the release of ghrelin.
  • An increase in energy stores triggers the release of leptin, which counteracts feelings of hunger. Leptin also inhibits the neurotransmitter anandamide. Anandamide is known to stimulate hunger and attaches to endogenous cannabinoid receptor sites (specifically a receptor known as the CBC1 receptor). When THC binds to these anandamide receptors in the brain, there is a decrease in leptin, which results in an increase in feelings of hunger.
  • THC also binds to receptors in the olfactory bulb in the brain that are noted to increase odor detection and food intake in mice (and probably have the same function in humans). This leads to an increased ability to smell, and this increased ability to smell makes food taste better (particularly when food is chewed, as it forces air through the nasal passages and increases both the sensations of smell and taste). When food tastes better, people tend to eat more of it.
  • THC also increases the palatability of sugary foods when it binds to the CB1 receptor site. Thus, individuals are more likely to gorge on sweeter tasting foods when they use marijuana.
  • When stimulated, the CB1 receptor site also produces increases in dopamine in an area called the nucleus accumbens. This area of the brain is part of the reward pathway that produces feelings of euphoria when certain behaviors are repeated. Thus, when the CB1 receptor site is activated by THC, it increases hunger and the reinforcement sensation associated with eating.
  • These overall effects are so strong that they simulate the feeling that an individual is actually starving and results in individuals often gorging on food.

Although most individuals would probably think that gorging on pastry, peanut butter, ice cream, etc., after using marijuana is a negative side effect of the use of cannabis products, this side effect of increasing hunger is extremely useful in treating individuals who have lost weight due to decreased appetite as a result of chemotherapy or having diseases like HIV. Cannabis products can increase appetite in these individuals and help them maintain a healthier weight, which can affect their recovery in a positive manner.

Bloodshot Eyes

A classic indicator that an individual may have used marijuana products is bloodshot or red eyes. Bloodshot or red eyes is actually an aspect of a therapeutic use of cannabis (or THC itself) in the treatment of glaucoma, a disorder of the optic nerve that has been associated with increases in intraocular pressure in the eyes. The use of THC may help to decrease this pressure and slow the progression of the damage.

THC has the effect of dilating blood vessels and capillaries, and lowering blood pressure. This results in increased blood flow in all areas of the body, including the eyes, and this reduces the pressure in the eyes. The increased blood flow in the eyes is responsible for the redness that occurs, whereas the decreased pressure is a result of the dilation of arteries and capillaries, and might be an effective treatment for glaucoma.

This effect is dose-dependent. Depending on the potency of the THC in marijuana, it may produce differing effects in individuals, such that if individuals consume low-potency THC strains of marijuana, it will not be as evident. However, when very high-potency forms of cannabis are ingested, such as edible cannabis products, the effect will be quite evident. Thus, simply smoking marijuana products is not necessarily associated with having red eyes because this effect can be clearly seen in individuals who use cannabis edibles, which typically have higher concentrations of THC than marijuana, which is smoked.

The Effects of Drugs

It also is possible that some individuals may develop an allergy to the byproducts associated with smoking cannabis products, and this can affect their eyes; however, this is a far rarer instance. Most often, it is not the smoke from marijuana that results in bloodshot eyes but the potency of the THC in the product.

Dry Mouth

Another telltale symptom associated with cannabis use is dry mouth (sometimes referred to as cottonmouth and technically known as xerostomia). This side effect has been the subject of numerous research studies and again involves the cannabinoid receptors in the body.

The cannabinoid receptors CB1 and CB2 are located in the brain and also in the submandibular glands found beneath the bottom of the mouth that are responsible for producing nearly three-quarters of saliva. When THC binds to these receptors, these glands stop receiving messages from the peripheral nervous system (in this case, the parasympathetic nervous system), and there is a reduction in the production of saliva. THC also binds to these receptor sites in the brain, and this also reduces the production of saliva.

Ways to Potentially Counteract Some of These Effects

For individuals who use marijuana medicinally, the above side effects can be quite exasperating. There are several ways to counteract these side effects that may or may not be useful, depending on the situation.

  • Use of low-potency THC strains of cannabis products can reduce some of the side effects associated with using cannabis. However, this may also reduce some of the therapeutic effects that individuals are attempting to achieve.
  • Use of eye drops is recommended for individuals who use marijuana medicinally if they want to avoid red eyes.
  • Drinking plenty of fluids can help to relieve some issues with dry mouth, red eyes, and even hunger. Individuals who use marijuana medicinally should remain hydrated.

Recreational users of cannabis products who suffer from these issues are advised to get into a recovery program for a cannabis use disorder.