How Does Marijuana Affect You?

If you’ve ever smoked a joint or eaten a pot-laced brownie, you’re hardly alone: More than 1 in 3 people in America have tried marijuana at one point in their lives.

Though occasional use isn’t usually harmful, pot can affect your body and mind any time it gets into your system. Here’s what you need to know.

Physical Effects

Marijuana comes from the hemp plant Cannabis sativa. It has an active ingredient called THC that makes you feel high. THC and other compounds in marijuana can also affect the way your body works.

Most people smoke the plant's dried leaves, flowers, stems, and seeds. But marijuana can also be mixed into food (like brownies, cookies, and lollipops), brewed as a tea, or inhaled with a vaporizer.

No matter how it gets into your system, it affects almost every organ in your body, and your nervous system and immune system, too. When you smoke pot, your body absorbs THC right away. (If you eat a baked good or another item, it may take much longer for your body to absorb THC, because it has to break down in your stomach before it enters your bloodstream). You may notice changes in your body right after you smoke. The effects usually stop after 3 or 4 hours.

Smoking pot can increase your heart rate by as much as two times for up to 3 hours. That’s why some people have a heart attack right after they use marijuana. It can increase bleeding, lower blood pressure, and affect your blood sugar, too.

We don’t yet know if marijuana is linked to higher odds of getting lung cancer. But the process does irritate your lungs -- which is why regular pot smokers are more likely to have an ongoing cough and to have lung-related health problems like chest colds and lung infections.

Other physical effects of marijuana include:

  • Dizziness
  • Shallow breathing
  • Red eyes and dilated pupils
  • Dry mouth
  • Increased appetite
  • Slowed reaction time (If you drive after using marijuana, your risk of being in a car accident more than doubles.)

If you’re a long-time user, you can have physical withdrawal symptoms -- like cravings, irritability, sleeplessness, and less appetite -- when you stop.


Changes to Mind and Mood

Most people use marijuana because the high makes them feel happy, relaxed, or detached from reality.

Smoking pot can also have less-pleasant effects on your mind and mood, too. You might have:

  • A distorted sense of time
  • Random thinking
  • Paranoia
  • Anxiety
  • Depression
  • Short-term forgetfulness

These effects usually ease up a few hours after you’ve used the drug.

Risks of Marijuana Use

Though you may have heard otherwise, marijuana can be addictive: Nearly 10% of people who use it become dependent on it. It isn’t clear whether marijuana is a gateway drug that makes people more likely to try harder drugs like cocaine and heroin.

The amount of THC in marijuana has gone up in recent years. Most leaves used to contain between 1% and 4% THC. Now most have closer to 7%. Experts worry this might make it easier to become dependent on or addicted to marijuana -- and it also strengthens many of the drug’s mind-altering effects.

Even if you buy from a legal, state-regulated dispensary, it can be hard to know exactly how much THC or other compounds found in marijuana you’re ingesting, so the effects can be unpredictable.

Marijuana can also cause more health problems if you have a condition like liver disease, low blood pressure, or diabetes.

If you’re a man, heavy use could lower your testosterone levels, and your sperm count and quality. That, in turn, can zap your libido and fertility.

Research shows a link between marijuana use and mental health problems like depression, anxiety, suicidal thoughts, short-term psychosis, and schizophrenia. While it’s not clear if marijuana causes these conditions, it can make them worse.

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on October 18, 2016



Gallup Analytics: “In U.S., 38% Have Tried Marijuana, Little Changed Since '80s.”

Harvard Medical School: “Medical Marijuana and the Mind.”

National Institute on Drug Abuse: “Drug Facts: Marijuana.”

Mayo Clinic: “Marijuana (Cannabis sativa)."

National Highway Traffic Safety Administration: “Cannabis/Marijuana.”

Melamede, R. Harm Reduction Journal, October 2005.

Tashkin, D. Annals of the American Thoracic Society, June 2013.

National Institute on Drug Abuse: “Cannabis (Marijuana): Health Effects.”

Johns, A., The British Journal of Psychiatry, 2001.

Morral, A. Addiction, October 2001.

Rand Corporation, Research Briefs: “Using Marijuana May Not Raise the Risk of Using Harder Drugs.”

Mary-Ann Fitzcharles, MD, associate professor of medicine in the department of rheumatology and McGill pain management unit at McGill University in Canada.

Stuart L. Silverman, MD, attending physician at Cedars-Sinai Medical Center in Beverly Hills, CA.

Brown, T. Journal of Clinical Pharmacology, November 2002.

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