Health effects of cannabis

Effects can be felt within seconds to minutes of smoking, vaporizing or dabbing cannabis. These effects can last up to 24 hours.

If you eat or drink cannabis, these effects can occur within 30 minutes to 2 hours and can last up to 24 hours.

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Short-term health effects

The flowers and leaves of the cannabis plant are used for their ability to cause effects on the mind, including:

  • feeling high (euphoria)
  • a sense of well-being
  • relaxation
  • heightened sensory experiences:
    • sight
    • taste
    • smell
    • sound

While cannabis may make you feel relaxed and happy, your body and brain may also experience effects that are:

  • negative
  • unwanted
  • unpleasant

Some of the short-term effects on your brain can include:

  • confusion
  • sleepiness (fatigue)
  • impaired ability to:
    • remember
    • concentrate
    • pay attention
    • react quickly
  • anxiety, fear or panic

Short term effects on your body can also include:

Cannabis use can also result in psychotic episodes characterized by:

  • paranoia
  • delusions
  • hallucinations

Long-term health effects

Long-term effects develop gradually over time, with daily or near-daily (weekly) use that continues over:

  • weeks
  • months
  • years

The long-term effects of cannabis on your brain can include an increased risk of addiction. Long-term cannabis use can also harm your:

Effects appear to be worse if you:

These effects can last from several days, to months or longer after you stop using cannabis. They may not be fully reversible even when cannabis use stops.

Other long-term effects of smoking cannabis are similar to the effects of smoking tobacco. These effects can include risks to lung health, such as:

  • bronchitis
  • lung infections
  • chronic (long-term) cough
  • increased mucus buildup in the chest

Health effects during pregnancy and breastfeeding

Just like with tobacco and alcohol, a pregnant woman or new mother's use of cannabis can affect her fetus or newborn child.

The substances in cannabis are carried through the mother's blood to her fetus during pregnancy. They are passed into the breast milk following birth. This can lead to health problems for the child.

Cannabis use during pregnancy can lead to lower birth weight of the baby. It has also been associated with longer-term developmental effects in children and adolescents, such as:

  • decreases in:
    • memory function
    • ability to pay attention
    • reasoning and problem-solving skills
  • hyperactive behaviour
  • increased risk for future substance use

Potential therapeutic uses of cannabis

There is some evidence of potential therapeutic uses for cannabis or its component chemicals (cannabinoids).

Health Canada has information for health care professionals and for authorized patients on the use of cannabis and cannabinoids for medical purposes. This includes information on:

  • potential therapeutic uses
  • dosing
  • warnings
  • adverse effects
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