THC is the most commonly known and most powerful chemical found in marijuana.

Marijuana is identified by its two active ingredients or chemicals: THC (tetrahydrocannabinol) and CBD (cannabidiol). THC is the psychoactive chemical that affects how you feel by creating the “high.” The amount and strength of THC depends on a number of factors, including the strain of cannabis and the conditions in which the plant grows. THC is also the best studied of the cannabinoid compounds in marijuana. When marijuana is taken into your system by either smoking or eating it, the chemicals it contains are introduced directly into your body. But how THC is delivered is only one part of the equation, the other is how it affects you. The most immediate effects of THC may be sensory or mood-changing, but there are other side effects that you should know about.

How Does THC Work?

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There are several ways of consuming marijuana: smoking, vaporizing (“vaping”) or ingesting it by mouth as an edible or concentrate. Smoking is the most common way of using marijuana and the fastest way of delivering THC and the other chemicals into the body. When marijuana is inhaled, THC goes directly to the lungs and enters the bloodstream. The lungs are able to absorb the smoke just seconds after inhalation, due to their enormous surface area covered with millions of air sacs. These tiny air sacs (alveoli) readily enable THC to enter the bloodstream. Once in the blood, THC quickly crosses the blood-brain barrier and enters the brain. Vaporizers offer an inhalable alternative to smoking by heating and turning the active chemicals in marijuana into a vapor. Like smoking, once vaporized and inhaled, THC enters the bloodstream and reaches the brain seconds later. Edibles (baked goods, teas, or tinctures) tend to be high in THC potency and strength. When edibles are eaten, THC is slowly absorbed into the bloodstream by the digestive system. Edibles may last longer and feel more intense than smoking or vaporizing. While the effects of inhaling THC will last from 45 minutes to a few hours, edibles can last for 6 to 8 hours or more.

THC and Your Brain

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When THC enters the brain, it stimulates cells to release dopamine. THC also activates pathways called cannabinoid receptors, which can affect the brain in many ways. The effects of THC include an initial relaxed and mellow feeling, eyes may dilate and other senses may be enhanced. Other reported effects include a mix of feelings such as elation or happiness, anxiety or unease, relaxation and, when used medicinally, pain relief. THC can also change thinking, memory, perception of time, and cause hallucinations or delusions. The more immediate effects of THC are typically felt 10 to 30 minutes after consumption. These initial effects on the brain may wear off in an hour or two, but the chemicals themselves stay in the body much longer. The half-life of marijuana or the length of time it stays in the body ranges from 24 hours to 10 days, depending on the amount of THC consumed.

What are the Psychoactive Effects of THC?

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Marijuana is one of the most common recreational drugs used to alter a person’s state of mind. It is often used to achieve immediate feelings of euphoria, or the proverbial “high.” Psychological/psychoactive effects of THC include:
  • Feelings of euphoria and relaxation
  • Time distortion
  • Intensification of sensory experiences (e.g. while watching TV or listening to music)
  • Increased socialization (laughter and being talkative)
  • Increased appetite (the “munchies”)
Besides the high, there are other psychological effects of THC as well. These effects vary from person to person, depending on the strength and amount of marijuana used and how it is taken. The overall effect that THC has when consumed is a form of intoxication with generally positive feelings.

What are the Side Effects of THC?

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Along with the positive feelings that marijuana creates, there are negative side effects that can occur. Immediate effects of marijuana include not only changes in behavior and mood, but physical effects too. Common side effects of THC include:
  • Cognitive impairment (memory and attention)
  • Motor impairment (coordination, reaction time, driving)
  • Anxiety or panic attacks
  • Increased heart rate
  • Red/bloodshot eyes
  • Dry mouth
  • Dizziness
  • Sedation or drowsiness
In severe cases/overdose:
  • Agitation
  • Nausea and vomiting
  • Psychosis (paranoia, delusions or hallucinations)
The most unpleasant and common side effect associated with occasional marijuana use is anxiety or panic reactions. Marijuana use can also have a negative impact on short-term memory, attention span, motor skills, reaction time and skilled activities like driving. Generally speaking, recreational doses of THC can affect driving performance similar to that of alcohol use. Studies on the effects of marijuana on driving have shown more modest impairment because cannabis users tend to be more aware of their intoxication. In extreme cases (such as overdose), consuming THC can lead to severe effects such as nausea, paranoia, agitation or hallucinations. Certain side effects of marijuana are more common than others. Frequent users can also develop a tolerance and may experience less side effects as a result.

What are the Long-Term Effects of THC?

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THC can have possible long-term effects for those who are chronic or regular cannabis users. Possible long-term effects of THC include:
  • Lung problems (such as bronchitis)
  • Heart problems
  • Cognitive impairments
  • Addiction/dependence
  • Withdrawal
In heavy users of cannabis, traces of THC may be detected weeks after they stop taking it. Additionally, some changes or decline in cognitive skills may not reverse themselves even after cessation or stopping cannabis use.

Lung Problems

Marijuana smokers may suffer from daily cough, phlegm, more constant cold and/or bronchitis. Smoking marijuana can also compromise the lung’s immune defenses and increase the risk of infection. Smoking marijuana relaxes and enlarges the bronchial passageways in the lungs. While not all cannabis users experience serious lung conditions, some of the more common respiratory ailments may result from irritation of the airways and chronic use. The smoke from marijuana itself contains 50 to 70% more carcinogenic hydrocarbons than tobacco smoke. So far, however, no definitive links have been made between marijuana use and lung cancer. Using a vaporizer can decrease the amount of toxins delivered into the lungs and may limit some of the common respiratory symptoms experienced by cannabis smokers.

Heart Risks

After ingesting marijuana, the heart rate can increase dramatically and remain elevated for up to 3 hours. Cannabis smoking can increase heart rate by 20 to 100%, increase blood pressure while sitting and decrease blood pressure when standing. For anyone with high blood pressure, heart arrhythmia or other cardiac disease, the risk of altered heart rhythms or heart attack may be increased.

Other Long-Term Issues

Chronic marijuana use has been associated with ongoing impairments of attention, memory, decision making, and social behavior. There is evidence that these effects are also dose-dependent. In other words, longer and earlier exposure to THC may lead to greater deficits. Heavy marijuana use may also contribute to lower expectations and poor relationship choices.

Addiction and Withdrawal

THC is also potentially addictive, based on feelings of craving or seeking out marijuana even when there may be negative social consequences. Repeated doses or intake of marijuana can lead to tolerance, which means less of the effects are felt and it takes a heavier or stronger dose to get the same euphoric feelings. Long-term marijuana users may experience withdrawal symptoms if they stop using it. These include irritability, decreased appetite, sleeplessness, drug craving and anxiety.

What Happens If You Ingest Too Much?

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Over the past few decades, the average THC content of cannabis has increased as well as the potency or strength of the cannabis being used today. Stronger strains of marijuana may increase your exposure to THC and the risk of adverse side effects. There are no reports of people fatally overdosing on marijuana. While too much marijuana does not lead to death, it can cause some very uncomfortable reactions, especially when associated with high THC levels.

Severe Side Effects

Severe side effects such as unease, shaking and, in rare cases, an extreme psychotic reaction may result from ingesting THC and may lead some to seek treatment at a hospital emergency room. Psychotic symptoms (paranoia, delusions or hallucinations) resulting from an overdose of THC generally last for a short duration, but some cases of overdose have been known to last for several days. This is usually caused by overconsumption and often follows from the ingestion of an edible. It’s all too easy to eat a couple of cookies or baked goods infused with cannabis extract without realizing how much THC is being consumed. Another way of inhaling marijuana is by dabbing. THC-rich resins are extracted from the cannabis plant and various concentrates like hash, butane honey oil, wax, budder or shatter are created to consume. These concentrates have the potential to deliver extremely large amounts of THC to the body and could result in more severe effects.

How To Prevent Overdose

To avoid a THC overdose, be sure of the amount that is being taken and keep it low, especially when unsure about the cannabis product. Drink lots of water to offset some of the uncomfortable effects like dry mouth and take it in a place where it feels safe to do so. Avoid combining cannabis with other drugs or alcohol. To check for an overdose, the person’s heart rate and other vital signs like breathing should be monitored. Always consult with a health professional before consuming THC. When considering cannabis, users should be aware of both the positive and negative effects of THC.