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What is THC and How Does It Affect People?

Marijuana is the most commonly used illicit drug in the United States, and for a good reason – its main psychoactive chemical, tetrahydrocannabinol (THC), can produce various pleasurable effects. But what does THC do to the brain?

WeedSociety Article on THC, Chemical Structure of THC graphic

THC is a cannabinoid (phytocannabinoid), meaning it interacts with receptors in the brain that are naturally activated by cannabinoids made by the body (endocannabinoids). These receptors are found in areas of the brain that influence pleasure, memory, thinking, concentration, and coordination. When THC binds to these receptors, it triggers a series of events that ultimately lead to the “high” associated with marijuana use.

How Tetrahydrocannabinol Affects The Brain

Cannabinoid receptors are concentrated in some regions of the brain associated with thinking, memory, pleasure, coordination, and time perception. According to NIDA, tetrahydrocannabinol attaches to these receptors and activates them, affecting a person’s memory, happiness, movements, thinking, concentration, coordination, and sensory and time perception. 

THC is one of many compounds found in the resin secreted by glands of the marijuana plant. More of these glands are located around the plant’s reproductive organs (buds) than on any other area of the plant. When cannabis is consumed, THC enters the bloodstream and eventually makes its way to the brain, which binds to cannabinoid receptors. This causes the “high” that people experience when they consume marijuana. 

The short-term effects of tetrahydrocannabinol include: 

  • -Euphoria
  • -Altered senses
  • -An altered sense of time 
  • -Changes in mood 
  • -Impaired body movement 
  • -Laughter
  • -Impaired memory 
  • -Hunger

Some People are susceptible to:

  • -Hallucinations (when taken in high doses) 
  • -Delusions (when taken in high doses) 
  • -Psychosis (when taken in high doses) 


As you can see, THC can have a wide range of effects on the brain. Some of these effects can be beneficial (such as pain relief), while others can be negative (such as impaired memory). It’s important to remember that everyone reacts differently to THC; what may cause one person to feel relaxed may cause another person to feel anxious or paranoid. If you’re planning on consuming cannabis with tetrahydrocannabinol, start with a low dose and gradually increase your intake until you find your sweet spot.

What are the Medical Benefits of THC?

THC and its associated cannabinoids have been shown to provide relief from a variety of conditions, both chronic and acute. In general, cannabinoids seem to help reduce pain, inflammation, and nausea. They may also help treat epilepsy, anxiety, glaucoma, HIV/AIDS symptoms, inflammatory bowel disease, and irritable bowel syndrome. More research is needed to determine the benefits of cannabis or cannabinoids for other conditions.

Pain relief is one of the most well-known benefits of THC and cannabinoids. Studies have shown that they can help decrease opioid use in patients with chronic pain. One study showed that after six weeks of treatment with THC-based medication, patients were able to reduce their opioid dosage by almost half.

Anxiety is another condition that tetrahydrocannabinol and cannabinoids may help. One small study showed that THC-rich cannabis reduced anxiety in patients with social anxiety disorder. More extensive studies are needed to confirm these findings.

Glaucoma is a condition that THC and cannabinoids may help. One study showed that cannabis reduced pressure in the eyes of people with glaucoma. However, more research is needed to determine whether tetrahydrocannabinol or other cannabinoids help treat glaucoma.

There is evidence that THC may benefit people with HIV/AIDS. One small study found that smoked cannabis was associated with a statistically significant increase in weight gain and improved food intake. A more substantial, placebo-controlled study found that dronabinol (a synthetic form of tetrahydrocannabinol) was associated with increased appetite and weight gain in patients with HIV/AIDS.

THC may also benefit people with inflammatory bowel disease (IBD). A small study found that THC improved symptoms in patients with IBD, and a bigger, placebo-controlled study found that THC was associated with decreased Crohn’s disease symptoms.

There is evidence that THC may benefit people with irritable bowel syndrome (IBS)A small study found that THC improved symptoms in patients with IBS, and a more significant, placebo-controlled study found that THC was associated with decreased abdominal pain.

THC and its compounds have been shown to relieve many symptoms related to movement disorders, including Tourette SyndromeA study published in the Journal of Clinical Neurology showed that THC could reduce tics in patients with Tourette Syndrome. In addition, a study published in the journal PLoS One showed that CBD was effective at lowering tics and improving the quality of life for patients with Tourette Syndrome.

THC has also been shown to be effective at treating multiple sclerosis (MS), and this disease affects the central nervous system. A study published in the journal Neurology showed that THC could reduce muscle spasms and improve mobility in patients with MS. In addition, a study published in the journal of Phyto-medicine showed that tetrahydrocannabinol was effective at reducing inflammation and pain in patients with MS.