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Everything you need to know about THC including 4 health benefits, potential risks, and how long it stays in your system


weed thc marijuana cbd cannabis
THC is one fo the main cannabinoid's found in marijuana.
Olena Ruban/Getty Images
  • THC is a cannabinoid that activates neurons responsible for pleasure, memory, and thinking.
  • THC differs from CBD in that it causes you to feel "high" and is illegal in many states. 
  • Potential health benefits of THC include managing pain and helping people sleep. 
  • Visit Insider's Health Reference library for more advice.

Short for tetrahydrocannabinol, THC is the component in marijuana responsible for the plant's psychoactive effects. When you feel "high" after using marijuana, that's because of THC. 

THC is a cannabinoid, a category of chemicals that interact with the body's endocannabinoid system. By attaching to cannabinoid receptors in the brain, THC activates neurons that influence pleasure, memory, thinking, coordination, and time perception. 

Some research and anecdotal evidence indicate THC may be used to treat a range of medical conditions. And from a recreational standpoint, it can feel good, causing a sensation of euphoria and relaxation in some. 

Here is what you need to know about THC from how it differs from CBD to its therapeutic uses. 


After THC, CBD is the most prevalent cannabinoid in marijuana. 

Unlike THC, CBD won't get you high. That's because CBD does not stimulate cannabinoid receptors in the brain like THC, says Jordan Tishler, MD, President of the Association of Cannabis Specialists. Instead, it changes how those receptors react to THC. For example, researchers have found CBD can weaken THC's anxiety-causing effects.

Another difference between THC and CBD is legality. In the United States, cannabis is federally illegal. However, on the state level legality varies

  • 16 states, Guam, Puerto Rico, and the District of Columbia have legalized small amounts of marijuana for recreational use
  • 27 states and the District of Columbia have decriminalized small amounts of marijuana
  • 19 states have legalized medical marijuana only 

As for CBD's legality? It's complicated.

CBD from industrial hemp (or cannabis with less than 0.3% THC) is legal, but CBD obtained from marijuana (cannabis with more than 0.3% THC) can only be used in states where weed is legal. 

How long does THC stay in your body?  

THC will build up in your system over time, so how frequently you use THC determines how long it remains in your body. In general, THC can be detected in infrequent users for one to three days after last use and 30 days or longer in chronic users. 

Your method of consumption plays a role, too: For example, your body takes longer to process the THC in an edible, meaning it will stay in your system longer than vaping or smoking. 

Here's how long THC can be detected in your system using various testing methods: 


Infrequent Users

Frequent Users

Chronic Users 

Blood Test

1 to 2 days 

7 days 

7 days 

Urine Test

1 to 3 days 

7 to 21 days 

30+ days 

Saliva Test

24 hours 

30 hours 

30 hours 

Hair Test 

90 days

90 days

90 days

4 Benefits of THC 

THC is used medicinally to relieve symptoms of certain conditions. But, because cannabis is federally illegal in the United States, research on THC is significantly limited.

"Most of the clinical data we have is anecdotal evidence or evidence from practitioners in states where they allow medical marijuana," says Amol Soin, MD, the medical director of the Ohio Pain Clinic and member of the Ohio Medical Marijuana board. "Marijuana is a [DEA] schedule one substance, which eliminates the ability to do a lot of clinical trial work."

Here are some of the emerging benefits, researchers have found so far: 

1. Alleviates pain

Chronic pain relief is the most common reason why people seek medical marijuana. A large 2015 systematic review evaluated cannabis studies in patients with chronic pain and found THC increased the odds for pain improvement by around 40%. 

While clinical trials support the use of cannabis for chronic pain, researchers agree more studies are needed to determine what doses, forms, and combinations of cannabinoids are most therapeutic for chronic pain patients. 

2. Reduces nausea from chemotherapy

Two oral THC-containing drugs — nabilone and dronabinol — have been available for the treatment of chemotherapy-induced nausea and vomiting for more than 30 years

A small 2010 study of chemo patients found those who took a THC-containing medicine in combination with standard treatment experienced stronger protection against nausea and vomiting than patients who received the standard treatment alone. 

3. Reduces muscle spasms in paraplegics

Studies suggest THC products can modestly reduce muscle spasms, a common symptom experienced by people with Multiple Sclerosis (MS) and paraplegia. 

In fact, a large 2015 systematic review concluded that THC used in combination with other cannabinoids improved self-reported muscle spasms more than a placebo, although the difference was not statistically significant. 

4. Improves sleep 

Sleep disturbances are typical in people living with health problems like MS and chronic pain. Studies in these groups show THC products can improve short-term sleep problems, reduce sleep disturbances, and decrease the time it takes to fall asleep. However, it's unclear whether the THC directly affects sleep quality or whether sleep is improved because chronic symptoms were reduced. 

Insider's takeaway 

THC is the active ingredient in marijuana responsible for making you feel high. Some studies indicate it can relieve chronic pain and other health problems. 

But, THC isn't all good — for some it can be addictive, and, while, you can't fatally overdose on THC, consuming too large of a dose could trigger uncomfortable side effects, including paranoia, anxiety, dry mouth, and nausea or vomiting

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