Marijuana (Cannabis, Weed)

Marijuana is a mind-alerting substance that comes from the Cannabis sativa plant. It has several short-term and long-term effects, many of which scientists are still studying.

Short-term effects of marijuana may include dizziness, altered senses, impaired memory, nausea, dry mouth and more.
The effects you might experience from marijuana aren’t always the same as what someone else might feel.

What is marijuana?

Marijuana is a substance that has mind-altering effects. Other names for marijuana include weed, pot and dope. Although people often use the terms “marijuana” and “cannabis” interchangeably, there are differences:

  • Cannabis: This term refers to all products derived from the Cannabis sativa plant. This includes its dried flowers, leaves, stems and seeds. The plant contains over 500 chemical substances. Cannabidiol (CBD) is one of these chemicals.
  • Marijuana: This term refers to parts of or products from the Cannabis sativa plant that contain substantial amounts of tetrahydrocannabinol (THC). This is the main chemical (cannabinoid) that causes mind-altering effects (makes you feel “high”).

In other words, marijuana is cannabis, but not all forms of cannabis are marijuana (contain THC).

Marijuana is one of the most used drugs in the United States, particularly among young adults. In 2021, 35.4% of people aged 18 to 25 (11.8 million people) reported using marijuana in the past year.

Scientifically, there are many unknowns regarding marijuana. Researchers are still studying the long-term and short-term effects of this substance.

Is marijuana a hallucinogen?

Scientists have historically classified marijuana (THC) as a hallucinogen. However, not all instances of marijuana use cause hallucinogen-like effects.

When people do experience hallucinations from marijuana use, they’re typically different from hallucinations people experience from other hallucinogens (like LSD, psilocybin and ecstasy). This suggests that the hallucinatory effects of marijuana may work differently from those of other hallucinogens.


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What is medical marijuana?

Several states in the U.S. have laws regarding the use of marijuana for medical purposes. These purposes are mainly to help with symptom management, not to directly treat a condition. Medical uses of marijuana may include:

The U.S. Food and Drug Administration (FDA) classifies marijuana as a Schedule I substance. This means that it has no currently accepted medical uses and a high potential for addiction. Because of this, healthcare providers can’t prescribe marijuana. But providers may certify marijuana use to help with certain medical conditions in states that legally allow it.

The FDA hasn’t approved marijuana to treat any medical conditions. But it has approved certain purified substances derived from marijuana (analogs).

FDA-approved analogs of marijuana include:

Not all hospital systems and healthcare providers certify medical marijuana in states where it’s legal. This is mainly due to the lack of thorough research and clinical trials on the medical uses of marijuana.

What are the effects of marijuana?

Marijuana affects each person differently based on several factors, like:

  • Your genetics.
  • Your age.
  • Your sex assigned at birth.
  • The amount and strength of the marijuana.
  • How you consume marijuana/THC (smoking, vaping or ingesting).
  • How long you’ve used marijuana and/or how frequently you use it.
  • If you’re taking medications and/or other substances.

The effects you might experience from marijuana aren’t always the same as what someone else might feel. In addition, different instances of marijuana use can cause different effects in the same person.

Studies show that marijuana use has certain short-term and long-term effects. But researchers are still learning about these, especially long-term effects.

Short-term effects of marijuana

When you smoke marijuana, THC quickly passes from your lungs into your bloodstream. Your blood carries THC to the brain and other organs. Your body absorbs THC more slowly if you eat or drink it — you typically experience the effects after 30 minutes to one hour.

THC resembles a naturally occurring chemical in your body called anandamide. THC can “work” as anandamide and fit into anandamide receptors in certain parts of your brain. Thus, the THC in marijuana overly activates parts of your brain that contain the highest number of these receptors, leading to a series of effects.

Short-term effects of marijuana related to brain function may include:

  • Altered senses, like seeing brighter colors or smelling scents more intensely.
  • Altered sense of time and space.
  • Euphoria and mood changes.
  • Issues with thinking and problem-solving.
  • Impaired memory.
  • Disorientation and confusion.
  • Relaxation and/or sleepiness (sedation).
  • Dizziness.
  • Issues with coordination.
  • Slowed reaction time.
  • Experiencing a panic attack.

If you consume marijuana in high doses, you may experience:

  • Hallucinations (false perception of objects or events involving your senses).
  • Delusions (unshakable belief in something untrue).
  • Psychosis. Your risk of this is highest if you regularly use high-potency marijuana.

Other common short-term effects of marijuana may include:

  • Dry mouth.
  • Nausea.
  • Increased heart rate (for up to three hours after smoking).
  • Increase in appetite.

Long-term effects of marijuana

Researchers are still learning about the long-term effects of marijuana use. So far, studies show:

  • Using marijuana during adolescence or young adulthood — before your brain fully develops — may affect how your brain builds connections for certain functions, like attention, memory and learning. These effects may last a long time or even be permanent.
  • Smoking any product, including marijuana, can damage your lungs, increase your risk of bronchitis and scar small blood vessels. Smoking marijuana can also increase your risk of stroke, heart disease and other vascular diseases. Vaping THC-containing products is linked to lung injury and even death.
  • Frequent use of marijuana is linked to a higher risk of developing schizophrenia or other psychoses in people who are predisposed to these conditions.
  • Long-term users of high doses of THC are at risk for frequent, severe vomiting (cannabis hyperemesis syndrome).

Studies show long-term use of marijuana is associated with:


What are the benefits of marijuana?

Scientists and healthcare providers can’t state any general benefits of marijuana with certainty. This is because there isn’t enough research yet about the medical benefits of the substance, especially long-term effects. In addition, marijuana tends to affect different people in many different ways.

While individual people may report certain personal benefits, all of these factors make it difficult to come to any firm conclusions.

What are the risks of marijuana?

Aside from the immediate and long-term health effects of marijuana, other risks include:

  • Marijuana use is linked to an increased risk of motor vehicle crashes.
  • Marijuana use is associated with an increased risk of injury among adults over 65.
  • Some cannabis/marijuana products can be contaminated with microorganisms, pesticides or other harmful substances.
  • Some cannabis/marijuana products contain amounts of cannabinoids that differ substantially from what’s stated on their labels.

Cannabis use disorder

Approximately 1 in 10 adult users of marijuana develop cannabis use disorder. This is one type of substance use disorder (SUD). SUD is a mental health condition in which a person has a problematic pattern of substance use that causes distress and/or impairs their life. Severe SUDs are also known as addiction.

Adolescents using cannabis are four to seven times more likely than adults to develop cannabis use disorder.

Cannabis use disorder can significantly impact your health, relationships and overall quality of life. It’s crucial to seek help as soon as you develop signs of this condition.

Marijuana and pregnancy

The FDA strongly advises against the use of CBD, THC and marijuana in any form during pregnancy or while breastfeeding (chestfeeding).

Marijuana use during pregnancy may:

  • Affect fetal brain development. THC can enter the fetal brain from the pregnant person’s bloodstream. Studies show this exposure can affect attention, memory and problem-solving.
  • Increase the risk of a newborn with low birth weight.
  • Increase the risk for premature birth and potentially stillbirth.

Breastmilk can contain THC for up to six days after use. So, you should avoid marijuana use while breastfeeding. THC may affect your baby’s brain development.

Marijuana smoke contains many of the same harmful components as tobacco smoke. Because of this, you should avoid smoking marijuana around a baby or children.

A note from Cleveland Clinic

Marijuana has several short-term and long-term effects, many of which scientists are still studying. Because of this, it’s important to use caution with marijuana and other cannabis products. If you want to learn more about the potential medical uses of marijuana or are concerned you have marijuana use disorder, talk to your healthcare provider. They’re available to help.

Medically Reviewed

Last reviewed on 11/05/2023.

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