Marijuana Health Risks

Why could George Burns smoke cigars every day for 70 years, and live to the ripe old age of 100? Why do some people who exercise every day of their life drop dead on the basketball court before they are 50? When it comes to how lifestyle affects health, there will always be some mysteries. There are no guarantees when it comes to the issue of health. There are however, known risks that can lead to likely outcomes. This section will inform you of the medical risks and possibly dangerous health effects of using marijuana. How you weigh these facts is up to you.

Below are some important facts from the Canadian Centre on Substance Abuse (CCSA).

Links to Mental Illness

Marijuana use can change the brain chemistry that controls mood, which can lead to depression and anxiety.

    • Some studies show a link between marijuana use and mental illnesses like depression, bipolar disorder, and anxiety. These studies show the risk is higher for users who start using marijuana before age 15.
    • A lot of research concludes that the same factors (genetic, environmental, and social) that can cause mental health issues can also lead to marijuana use. Recent studies show that heavy marijuana use and depression occur together very often.  This has led some researchers to explore the idea that marijuana use may actually cause depression, especially in youth.
    • According to a study by Dr. Gabriella Gobbi from the Research Institute of the McGill University Health Centre, daily use of marijuana in teens may cause depression and anxiety and cause long-term changes to the brain that cannot be undone. Her study, that used rats, found that marijuana affects two chemicals in the brain, serotonin and norepinephrine.  These chemicals help control mood and anxiety. 
    • Dr. Gobbi’s study reported that adolescents who use marijuana have less serotonin transmission, which may lead to mood disorders.  They also show more norephinephrine transmisison, which can make them more prone to long-term stress. Adults who were exposed to cannabis did not have the same results. This is one of the first studies to show that marijuana use causes more serious damage during teen years than during adulthood.  More research is needed to better understand these possible connections. (Cannabis and adolescence: A dangerous cocktail)

    The Teen Brain


Marijuana vs. Tobacco Smoke

Marijuana smoke is similar to tobacco smoke, and contains many cancer-causing chemicals. 

  • Research to date is unclear about whether smoking marijuana leads is linked to lung cancer.  But we know that marijuana smoke contains a mixture of poisons that are similar to tobacco smoke. In fact, Marijuana smoke contains over 400 chemicals, and many of them are carcinogenic (cancer-causing). This fact, combined with the fact that tobacco smoke causes lung cancer, supports the need for further research on this topic.

    Marijuana and the Lungs

Breathing & Lung Risks

Researchers have found many similarities between the effects of marijuana smoking on the lungs compared to those of tobacco smoking.

    • Studies show that marijuana smoke is as harmful to the airways as tobacco, because the ‘tar content’ is similar for both types of smoke. Smoking marijuana may be even more harmful than tobacco smoking, since the technique for smoking marijuana involves unfiltered smoking, larger puffs, deeper breaths and longer breath-holding.
    • Breathing problems that can result from long-term marijuana smoking include:
      • coughing on most days,
      • wheezing,
      • shortness of breath after exercise,
      • night-time chest tightness,
      • chest sounds without a cold,
      • early morning phlegm and mucus, and
      • Bronchitis.
    • Another serious breathing condition that may be linked to marijuana smoking is “Chronic Obstructive Pulmonary Disease (COPD)”.  COPD is a lung disease involving damage to the air sacs in the lungs and the narrowing/blocking of the airways, making breathing difficult.
    • The THC from marijuana smoke that enters the lungs and airways increases the risk of lung conditions. One type of cell that THC affects is the alveolar macrophages, which are a main defense against infections in the lungs. A weak immune response in the lungs means that marijuana smokers are more likely to get sick from viral, bacterial, and fungal invaders. 

    Respiratory Effects of Cannabis Smoking

Marijuana and Pregnancy

Marijuana use during pregnancy may harm fetal growth, lead to low birth weight, and impact normal growth in childhood.

  • The chemicals in marijuana cross the placenta and reach the fetus. Exposing infants to marijuana in the womb can play a role in low birth weight. Research shows that that these children may experience behavioral and developmental effects during the first few months of life and later in childhood.

    Maternal Cannabis Use During Pregnancy

Marijuana Dependency

Marijuana use can lead to psychological or physical dependency on the drug.

  • Drug dependency means that a person needs the drug to function normally. People who use marijuana regularly can develop a psychological dependency, and people who use marijuana daily may develop a physical dependency. Someone who has a physical dependency may experience mild withdrawal signs if the drug is stopped abruptly.

    More on Dependency 

Marijuana production is not regulated, so there is no way to know how strong it is or what other substances it may contain. This can be very dangerous for the user.

Marijuana Health Risks

In 2010 David Suzuki’s show called “The Nature of Things” aired an episode on CBC-TV titled “The Downside of High”. 

See the program.
Marijuana Health Risks

Additional Resources