Physical Health Concerns

Within a few minutes after inhaling marijuana smoke, a person’s heart rate speeds up, the breathing passages relax and become enlarged, and blood vessels in the eyes expand, making the eyes look bloodshot (red). The heart rate—normally 70 to 80 beats per minute—may increase by 20 to 50 beats per minute or may even double in some cases. This page provides information on the physical effects marijuana can have on adults and adolescents.


Image of a marijuana leaf.

Effects On Adolescents (Age 14-18)

  • Chronic marijuana use during adolescence may result in an average decrease in IQ of 8 points.
  • Deficits may include impaired learning, memory, executive functions, and verbal fluency.
  • Deficits may not be fully reversible even with abstinence by age 22

Heavy marijuana use in puberty and mid-adolescence may have effects on brain structure and function that are different, more significant, and longer lasting than does use in adulthood. These effects include:

  • Cognitive deficiencies
  • Development of neuropsychiatric disorders
  • Likelihood of other substance use/abuse
  • Likelihood of cannabis dependence

Cardiovascular/Cerebrovascular Effects

  • Cardiovascular
    • Increased chest pain
    • Heart attack
    • Irregular heartbeats
    • Weakened heart muscle
  • Cerebrovascular
    • Mini-stroke
    • Stroke
  • These events are occurring in young persons with no other risk factors
  • Heart attack rate increases 4.8 times in first hour after marijuana use
  • 4.2 times increase in mortality rate in marijuana users compared with non-users following a heart attack

Respiratory Effects

  • Cannabis smoke contains many times more tar, carbon monoxide, and other toxic chemicals than tobacco
  • Effects include:
    • Cough
    • Chronic bronchitis
    • Lung infections
    • Obstructed airways

Other Physical Effects

  • Immune system abnormalities
    • Both positive and negative
  • Decreased testosterone, resulting in:
    • Testicular shrinkage
    • Breast enlargement ("man boobs")
    • Loss of interest in sex
    • Erectile dysfunction
    • Loss of muscle mass

Marijuana-Associated Adverse Health Outcomes

  • Chronic marijuana use/abuse is associated with:
    • Tobacco use
    • Alcohol use and abuse
    • Illicit drug abuse
    • Other risk-taking behaviors
      • Drunk driving
      • Sexual activity
  • Difficult to separate out cause and effect
    • Marijuana use may not cause other adverse health behaviors, but instead, may be part of a larger, risk-taking behavioral lifestyle
    • Nonetheless, marijuana use may be a marker for other behaviors of concern (i.e., a "red flag")

All information was obtained through research compiled in the 2017 report published by the National Academies of Sciences and Medicine titled The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations.

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