• Knowledgebase: Questions about Drugs and Tobacco

    Questions about drug use, for adolescents and their parents.


    6. Short and Long Term Effects of Marijuana - Top

    Q: What are the short-term effects of marijuana use?
    A: The short-term effects of marijuana include:

    problems with memory and learning;(11)


    distorted perception (sights, sounds, time, touch)(6);


    trouble with thinking and problem-solving;(5)


    loss of coordination; and


    increased heart rate, anxiety.

    These effects are even greater when other drugs are mixed with the marijuana; and users do not always know what drugs are given to them.

    Q: What are the long-term effects of marijuana use?
    A: Findings so far show that regular use of marijuana or THC may play a role in some kinds of cancer and in problems with the respiratory, and immune systems.


    Cancer
    It's hard to know for sure whether regular marijuana use causes cancer. But it is known that marijuana contains some of the same, and sometimes even more, of the cancer-causing chemicals found in tobacco smoke. Studies show that someone who smokes five joints per week may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day.(15)


    Lungs and airways
    People who smoke marijuana often develop the same kinds of breathing problems that cigarette smokers have: coughing and wheezing. They tend to have more chest colds than nonusers. They are also at greater risk of getting lung infections like pneumonia.


    Immune system
    Animal studies have found that THC can damage the cells and tissues in the body that help protect people from disease. When the immune cells are weakened, you are more likely to get sick.


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    Q: Does marijuana lead to the use of other drugs?
    A: It could. Long-term studies of high school students and their patterns of drug use show that very few young people use other illegal drugs without first trying marijuana. For example, the risk of using cocaine is 104 times greater for those who have tried marijuana than for those who have never tried it.(7) Using marijuana puts children and teens in contact with people who are users and sellers of other drugs. So there is more of a risk that a marijuana user will be exposed to and urged to try more drugs.

    To better determine this risk, scientists are examining the possibility that long-term marijuana use may create changes in the brain that make a person more at risk of becoming addicted to other drugs, such as alcohol or cocaine. While not all young people who use marijuana go on to use other drugs, further research is needed to predict who will be at greatest risk.


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    Q: How can you tell if someone has been using marijuana?
    A: If someone is high on marijuana, he or she might
    seem dizzy and have trouble walking;
    seem silly and giggly for no reason;
    have very red, bloodshot eyes; and
    have a hard time remembering things that just happened.
    When the early effects fade, over a few hours, the user can become very sleepy.

    - Updated: March 10, 2001

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  • James L Horwitz, MD

    David C. Thomas, MD

    Barbara Lindberg, PNP