Marijuana comes from a plant called hemp. Its scientific name is Cannabis sativa. The main, active ingredient in marijuana is THC (short for delta-9-tetrahydrocannabinol). This ingredient is found in the leaves and flowering parts of the marijuana plant. Hashish is a substance taken from the tops of female marijuana plants. It contains the highest amount of THC.
Marijuana is called by many other names, including cannabis, grass, hashish, joint, Mary Jane, pot, reefer, weed.
Some states in the United States permit marijuana to be used legally to treat certain medical problems. Other states have also legalized its recreational use.
This article is on the recreational use of marijuana, which may lead to abuse.
Marijuana's Effects on Your Brain
The THC in marijuana acts on your brain (central nervous system). THC causes brain cells to release dopamine. Dopamine is a chemical that is involved with mood and thinking. It is also called the feel-good brain chemical. Using marijuana may cause pleasurable effects such as:
- Feeling "high" (pleasant sensations) or very relaxed (marijuana intoxication)
- Having an increased appetite ("the munchies")
- Increased sensations of sight, hearing, and taste
How fast you feel the effects of marijuana depends on how you use it:
- If you breathe in marijuana smoke (such as from a joint or pipe), you may feel the effects within seconds to several minutes.
- If you eat foods containing the drug as an ingredient, such as brownies, you may feel the effects within 30 to 60 minutes.
Harmful Effects of Marijuana
Marijuana can also have unpleasant effects:
- It can affect your mood -- You may have feelings of panic or anxiety.
- It can affect how your brain processes things around you -- You may have false beliefs (delusions), become very fearful or confused, see or hear things that are not there (hallucinations).
- It can cause your brain not to work as well -- For example, you may not be able to concentrate or pay attention at work or at school. Your memory may weaken. Your coordination may be affected such as with driving a car. Your judgment and decision making can also be affected. As a result, you may do risky things such as drive while high or have unsafe sex.
Marijuana's other health effects include:
- Bloodshot eyes
- Increased heart rate and blood pressure
- Infections such as sinusitis, bronchitis, and asthma in heavy users
- Irritation of the airways causing narrowing or spasms
- Sore throat
- Weakening of the immune system
Marijuana can be Addictive
Some people who use marijuana get addicted to it. This means their body and mind are dependent on marijuana. They are not able to control their use of it and they need it to get through daily life.
Addiction can lead to tolerance. Tolerance means you need more and more marijuana to get the same high feeling. And if you try to stop using, your mind and body may have reactions. These are called withdrawal symptoms, and may include:
- Feeling fear, unease, and worry (anxiety)
- Feeling stirred up, excited, tense, confused, or irritable (agitation)
- Trouble falling or staying asleep
Treatment begins with recognizing there is a problem. Once you decide you want to do something about your marijuana use, the next step is getting help and support.
Treatment programs use behavior change techniques through counseling (talk therapy). Some programs use 12-step meetings to help people learn how not to relapse. The goal is to help you understand your behaviors and why you use marijuana. Involving family and friends during counseling can help support you and keep you from going back to using (relapsing).
If you have severe withdrawal symptoms, you may need to stay at a residential treatment program. There, your health and safety can be monitored as you recover.
At this time, there is no medicine that can help reduce the use of marijuana by blocking its effects. But, scientists are researching such medicines.
Your Ongoing Recovery
As you recover, focus on the following to help prevent relapse:
- Keep going to your treatment sessions.
- Find new activities and goals to replace ones that involved your marijuana use.
- Spend more time with family and friends you lost touch with while you were using marijuana. Consider not seeing friends who are still using marijuana.
- Exercise and eat healthy foods. Taking care of your body helps it heal from the harmful effects of marijuana. You will feel better, too.
- Avoid triggers. These can be people with whom you used marijuana. They can also be places, things, or emotions that can make you want to use marijuana again.
When to Call the Doctor
Call for an appointment with your health care provider if you or someone you know is addicted to marijuana and needs help stopping. Also call if you are having withdrawal symptoms that concern you.
Substance abuse - marijuana; Drug abuse - marijuana; Drug use - marijuana; Cannabis; Grass; Hashish; Mary Jane; Pot; Weed
Kowalchuk A, Reed BC. Substance use disorders. In: Rakel RE, Rakel DP, eds. Textbook of Family Medicine. 9th ed. Philadelphia, PA: Elsevier; 2016:chap 50.
National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana: An Evidence Review and Research Agenda. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington, DC: National Academies Press; 2017.
National Institute on Drug Abuse website. Marijuana. www.drugabuse.gov/publications/research-reports/marijuana/what-marijuana. Updated July 2020. Accessed August 17, 2022.
Weiss RD. Drugs of abuse. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 31.
Review Date 4/30/2022
Updated by: Fred K. Berger, MD, addiction and forensic psychiatrist, Scripps Memorial Hospital, La Jolla, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.