Health Topic

Marijuana

Marijuana contains the mind-altering chemical THC. Some U.S. states approve the use of medical marijuana. Read about marijuana and its effects.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Blunt · Cannabis · Dope · Ganja · Grass · Hash · Joint · Mary Jane · Pot · Reefer · Weed

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Marijuana

Marijuana is a green, brown, or gray mix of dried, crumbled parts from the marijuana plant. The plant contains chemicals which act on your brain and can change your mood or consciousness.

There are many different ways that people use marijuana, including:

  • Rolling it up and smoking it like a cigarette or cigar
  • Smoking it in a pipe
  • Mixing it in food and eating it
  • Brewing it as a tea
  • Smoking oils from the plant ("dabbing")
  • Using electronic vaporizers ("vaping")

Marijuana can cause both short-term and long-term effects.

While you are high, you may experience:

  • Altered senses, such as seeing brighter colors
  • Altered sense of time, such as minutes seeming like hours
  • Changes in mood
  • Problems with body movement
  • Trouble with thinking, problem-solving, and memory
  • Increased appetite

In the long term, marijuana can cause health problems, such as:

  • Problems with brain development. People who started using marijuana as teenagers may have trouble with thinking, memory, and learning.
  • Coughing and breathing problems, if you smoke marijuana frequently
  • Problems with child development during and after pregnancy, if a woman smokes marijuana while pregnant

It is possible to overdose on marijuana, if you take a very high dose. Symptoms of an overdose include anxiety, panic, and a rapid heartbeat. In rare cases, an overdose can cause paranoia and hallucinations. There are no reports of people dying from using just marijuana.

After using marijuana for a while, it is possible to get addicted to it. You are more likely to become addicted if you use marijuana every day or you started using it when you were a teenager. If you are addicted, you will have a strong need to take the drug. You may also need to smoke more and more of it to get the same high. When you try to quit, you may have mild withdrawal symptoms such as:

  • Irritability
  • Trouble sleeping
  • Decreased appetite
  • Anxiety
  • Cravings

The marijuana plant has chemicals that can help with some health problems. More states are making it legal to use the plant as medicine for certain medical conditions. But there isn't enough research to show that the whole plant works to treat or cure these conditions. The U.S. Food and Drug Administration (FDA) has not approved the marijuana plant as a medicine. Marijuana is still illegal at the national level.

However, there have been scientific studies of cannabinoids, the chemicals in marijuana. The two main cannabinoids that are of medical interest are THC and CBD. The FDA has approved two drugs that contain THC. These drugs treat nausea caused by chemotherapy and increase appetite in patients who have severe weight loss from AIDS. There is also a liquid drug that contains CBD. It treats two forms of severe childhood epilepsy. Scientists are doing more research with marijuana and its ingredients to treat many diseases and conditions.

It sits within Substance Use and Disorders.

The lead U.S. institute for this subject is the National Institute on Drug Abuse.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Marijuana

1,001 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Diagnosis and Tests

Treatments and Therapies

Prevention and Risk Factors

Related Issues

Statistics and Research

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Marijuana Use, Medical Marijuana, Marijuana Smoking, Marijuana Abuse. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Marijuana, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.