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What are the side effects of marijuana?

Medically reviewed by Last updated on Sep 8, 2020.

Official Answer


The most common side effects of marijuana include:

  • An increased heart rate or altered heart rhythm
  • An altered perception of time or a distorted response to touch, sights or sounds
  • An increased appetite
  • An impaired reaction time which may affect driving or task performance
  • Coordination difficulties
  • Difficulty in thinking and problem solving, poor memory
  • Dry mouth and/or dry eyes
  • Low blood pressure, which may cause dizziness when standing or increase the risk of falls
  • Slowed digestion which may lead to constipation.

Marijuana (cannabis) is a mixture of leaves, stems, seeds, and flowers of the hemp plant Cannabis sativa, and is used both recreationally and for certain medical ailments. Many US states have legalized the use of marijuana.

Side effects vary from person to person and depend on the potency and amount of marijuana used, as well as the frequency of use. People who are chronically exposed to THC (tetrahydrocannabinol), the active constituent in marijuana, are less likely to have side effects than those who have never used it or only use it occasionally.

Marijuana can cause short-term paranoia in some people, resulting in symptoms such as anxiety, agitation, confusion, panic attacks and occasionally, psychosis. These reactions may be more common in people with an underlying psychiatric disorder or who are genetically more susceptible to mental health disturbances.

Dependence on marijuana can arise with long-term use resulting in withdrawal symptoms. The risk of a heart attack is also increased in the hour following marijuana use; people with underlying heart conditions should use marijuana with caution. Marijuana smoke also contains cancer-causing chemicals in quantities higher than cigarette smoke. Respiratory problems, such as a persistent cough and phlegm, bronchitis, wheezing, shortness of breath, or an increased susceptibility to colds or other respiratory infections are common in marijuana smokers.

Users should also be aware that marijuana purchased off the street can sometimes be laced with other drugs or substances that can lead to more dangerous side effects.

For more information see Marijuana: Effects, Medical Uses and Legalization

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