The side effects of THC

THC (tetrahydrocannabinol) is the main psychoactive ingredient in cannabis. Simply stated, it is the part of the plant that gets you high. THC-rich cannabis strains can produce enjoyable sensations from mild relaxation to total euphoria. But does THC have any negative side effects?

Delta 9 THC compound
THC (tetrahydrocannabinol) is the main psychoactive ingredient in cannabis.

Here you'll learn about the possible unwanted short-term side effects of consuming too much THC, along with tips on how you can avoid these unwanted effects.

What are the general effects of THC?

The general effects of THC vary depending on the individual, but many people report feelings of happiness and bursts of energy from consuming cannabis. Some weed strains, like Cinderella 99 and Super Silver Haze, are even reputed to boost creativity

People who suffer from depression may find that THC is a mood lifter since cannabis use can raise serotonin levels in the brain. The possible relationship between cannabinoids like THC and serotonin could prove useful in treating mild depression, as higher serotonin levels correlate with better mood.

man vaping weed
Consuming THC in small to moderate amounts can result in positive effects and a better mood.
Photo by: Gina Coleman/Weedmaps

Bottom line: Consuming THC in small to moderate amounts can result in positive effects. But what occurs when you consume too much THC can look very different.

What happens when you consume too much THC?

First, how do you know if you're consuming too much THC? New cannabis users who have not yet figured out their tolerance level should start with a strain that has a potency of 10% THC or less or a 1:1 ratio of THC to CBD. Whichever strain you choose, you may also find it helpful to consume a smaller amount of cannabis until you know your limits. It can take up to 15 minutes to feel the full effects after inhaling, so pacing yourself is also a wise move. 

The general side effects of consuming too much THC range from mild to severe and may take the following forms:

  • Dry or bloodshot eyes
  • Dry "cotton" mouth
  • Hypothermia/shivering
  • Racing heartbeat
  • Impaired coordination
  • Impaired thinking/concentration/learning
  • Difficulty sleeping
  • Dizziness or vertigo 
  • Nausea and vomiting
  • Anxiety or panic attack
  • Paranoia
migraines and weed
The general side effects of consuming too much THC range from mild to severe, like racing heartbeat, vomiting, and paranoia.
Photo by: Gina Coleman/Weedmaps

In very rare cases, large amounts of THC can lead to extreme side effects. According to Dr. Adie Rae, a neuroscientist and scientific adviser to Weedmaps, these extreme side effects may include:

  • Psychotic-like symptoms (such as hallucinations or delusions)
  • Cardiac injury (one of the few potential long-term side effects of overconsuming THC)
  • Seizure 

People who consume cannabis on a frequent and/or heavy basis are more likely to experience the potential adverse effects of THC. Accordingly, cannabis strains with high levels of THC may pose a greater risk for acute negative health effects.

"The intensity and duration of all these effects is proportional to the dose of THC: the more in the bloodstream, the more likely you are to experience these side effects. You're more likely to have negative side effects from eating cannabis products compared to smoking flower. Ingesting concentrates is associated with the most dangerous and severe side effects,” says Dr. Rae. 

Bottom line: It's nearly impossible to overdose on THC but relatively easy to experience severe discomfort. In fact, it would probably take an estimated 240 joints to lethally overdose on marijuana, according to the 1997 book Cannabis in Medical Practice: A Legal, Historical and Pharmacological Overview of the Therapeutic Use of Marijuana. Even though serious side effects from THC overconsumption are few and rare, be sure to exercise caution when smoking and especially when trying edibles or concentrates. 

Studies on THC side effects

As with many cannabis-related topics, studies on the side effects of THC are limited. However, in line with Dr. Rae's assertions, one 2020 study published in the Canadian Medical Association Journal showed that issues with THC dosing in edible cannabis products could lead to negative effects. Edible consumption of THC delivers delayed results, leading many to over consume before the full effect sets in. Gauging doses of edibles is often difficult as well, especially with unregulated products. 

Bottom line: Recovering from ingesting too much THC or experiencing what is known as a “weed hangover” may include strategies like hydration, rest, and nutrition. But there are other ways you can prevent a weed hangover in the first place. 

How to avoid the side effects of THC

You may be able to avoid any negative side effects of THC by consuming in moderation and taking a few other precautionary measures. "To avoid negative side effects, start with a low dose, and increase slowly over time. For inhalation, that's one puff every 15 minutes. For edibles, wait at least two hours before ingesting any more, or just ride out the mellow experience and try a larger dose the next time around," Dr. Rae advised.

dab rig
In terms of consumption methods, some are more likely to induce unpleasant side effects than others, such as concentrates and edibles.
Photo by: Gina Coleman/Weedmaps

In terms of consumption methods, some are more likely to induce unpleasant side effects than others. According to Dr. Rae, concentrates are most dangerous and should be left to more experienced consumers. In fact, she recommends that those who can only experience a high from concentrates try taking a tolerance break

Bottom line: In moderation, the consumption of cannabis may offer a variety of therapeutic benefits, but over consuming can lead to problems. Start slowly, be aware of your marijuana tolerance levels, and adjust your consumption accordingly, remembering to consult with your physician before beginning a cannabis regimen.

Major contributions from Dr. Adie Rae.

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The information contained in this site is provided for informational purposes only, and should not be construed as medical or legal advice. This page was last updated on June 20, 2022.