The Effects of Marijuana

What is marijuana?

Marijuana refers to the dried leaves, flowers, stems, and seeds from the Cannabis sativa or Cannabis indica plant. The plant contains the mind-altering chemical THC and other similar compounds. Extracts can also be made from the cannabis plant (see “Marijuana Extracts”).

Marijuana is the most commonly used psychotropic drug in the United States, after alcohol. Its use is widespread among young people. In 2018, more than 11.8 million young adults used marijuana in the past year. According to the Monitoring the Future survey, rates of past year marijuana use among middle and high school students have remained steady, but the number of teens in 8th and 10th grades who say they use it daily has increased. With the growing popularity of vaping devices, teens have started vaping THC (the ingredient in marijuana that produces the high), with nearly 4% of 12th graders saying they vape THC daily. In addition, the number of young people who believe regular marijuana use is risky is decreasing.

Legalization of marijuana for medical use or adult recreational use in a growing number of states may affect these views. Read more about marijuana as medicine in our Drug Facts: Marijuana as Medicine.

How do people use marijuana?

People smoke marijuana in hand-rolled cigarettes (joints) or in pipes or water pipes (bongs). They also smoke it in blunts—emptied cigars that have been partly or completely refilled with marijuana. To avoid inhaling smoke, some people are using vaporizers. These devices pull the active ingredients (including THC) from the marijuana and collect their vapor in a storage unit. A person then inhales the vapor, not the smoke. Some vaporizers use a liquid marijuana extract.

People can mix marijuana in food (edibles), such as brownies, cookies, or candy, or brew it as a tea. A newly popular method of use is smoking or eating different forms of THC-rich resins (see “Marijuana Extracts”).

How does marijuana affect the brain?

Marijuana has both short-and long-term effects on the brain.

Short-Term Effects

When a person smokes marijuana, THC quickly passes from the lungs into the bloodstream. The blood carries the chemical to the brain and other organs throughout the body. The body absorbs THC more slowly when the person eats or drinks it. In that case, they generally feel the effects after 30 minutes to 1 hour.

THC acts on specific brain cell receptors that ordinarily react to natural THC-like chemicals. These natural chemicals play a role in normal brain development and function.

Marijuana over activates parts of the brain that contain the highest number of these receptors. This causes the “high” that people feel. Other effects include:

altered senses (for example, seeing brighter colors)
altered sense of time
changes in mood
impaired body movement
difficulty with thinking and problem-solving
impaired memory
hallucinations (when taken in high doses)
delusions (when taken in high doses)
psychosis (risk is highest with regular use of high potency marijuana)
Long-Term Effects

Marijuana also affects brain development. When people begin using marijuana as teenagers, the drug may impair thinking, memory, and learning functions and affect how the brain builds connections between the areas necessary for these functions. Researchers are still studying how long marijuana’s effects last and whether some changes may be permanent.

For example, a study from New Zealand conducted in part by researchers at Duke University showed that people who started smoking marijuana heavily in their teens and had an ongoing marijuana use disorder lost an average of 8 IQ points between ages 13 and 38. The lost mental abilities didn’t fully return in those who quit marijuana as adults. Those who started smoking marijuana as adults didn’t show notable IQ declines.

In another recent study on twins, those who used marijuana showed a significant decline in general knowledge and in verbal ability (equivalent to 4 IQ points) between the preteen years and early adulthood, but no predictable difference was found between twins when one used marijuana and the other didn’t. This suggests that the IQ decline in marijuana users may be caused by something other than marijuana, such as shared familial factors (e.g., genetics, family environment). NIDA’s Adolescent Brain Cognitive Development (ABCD) study, a major longitudinal study, is tracking a large sample of young Americans from late childhood to early adulthood to help clarify how and to what extent marijuana and other substances, alone and in combination, affect adolescent brain development.



  1. Reply

    Nice info, thanks for sharing

  2. Reply

    Thanks for sharing this post

  3. Reply


  4. Reply


  5. Reply


  6. Reply

    This z really bad

  7. Reply

    Thanks for sharing

  8. Reply


  9. Reply

    This is really good and interesting to know

  10. Profile photo ofItz Kvng Twitch


    Let them hear

  11. Reply

    Thanks for the update

  12. Reply

    Very helpful

  13. Reply

    Thanks for the update

  14. Reply

    Marijuana contains 302 chemical s which are harmful to the body system

  15. Reply

    Interesting thanks for the information

  16. Reply

    Cool info

  17. Reply

    Nice info

  18. Reply

    Very important

  19. Reply

    Thanks for sharing

  20. Reply

    Good to know

  21. Reply

    good one

  22. Reply


  23. Reply

    Thanks for sharing this update

  24. Reply

    Government should arrest anyone seen with marijuana without a hospital identification card

  25. Reply


  26. Reply

    Marijuana is a very hard drug that should generally be avoided.
    All other hard drugs as well. They have no positive benefits at all

  27. Reply

    Prevention is better than cure

  28. Reply

    Marijuana has more disadvantage than advantage

  29. Reply


  30. Profile photo ofcelestine


    Good update

  31. Reply

    good one

  32. Reply

    Nice to hear

  33. Reply


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