What is cannabis?

Cannabis, also known as marijuana, is a green, brown, or gray mixture of dried parts from the cannabis plant. The plant contains chemicals that affect the brain and can change how you feel or think.

The main active chemicals are cannabinoids, including:

• THC (tetrahydrocannabinol), which causes the "high"
• CBD (cannabidiol), which does not cause a high

How do people use cannabis?

There are many ways that people use cannabis, including:

• Rolling it up and smoking it like a cigarette ("joint") or cigar ("blunt")
• Smoking it in a pipe ("bowl") or water pipe ("bong")
• Mixing it into drinks like tea, or food like cakes or brownies ("edibles")
• Smoking concentrated oils ("dabbing")
• Using electronic vaporizers ("vaping")
• Taking liquid drops under the tongue ("tinctures")
• Applying it to the skin as lotions or balms ("topicals")

Topical products usually do not cause a high.

What are the effects of cannabis?

Cannabis can cause short-term and long-term effects. These can vary depending on:

• How much you use
• How often you use it
• The THC level
• The ingredients
• How you take it
• Other medicines or drugs used at the same time
• Other health conditions you have
• Your age and sex
• Your experience with cannabis

Short-term effects:

While you are high, you may notice:

• Changes in 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
• Slower reaction time

Secondhand smoke from cannabis products has many of the same risks as secondhand tobacco smoke.

Long-term effects:

In the long term, cannabis can cause health problems, which can include:

• Problems with brain development. People who started using cannabis as teenagers may have trouble with thinking, memory, and learning.
• Coughing and breathing problems, if you smoke cannabis frequently.
• Repeated episodes of nausea, vomiting, and stomach pain due to long-term, heavy cannabis use. This is called cannabinoid hyperemesis syndrome (CHS).
• Problems with fetal and child development during and after pregnancy, if you smoke cannabis while pregnant.

Heavy long-term use of cannabis has been linked to increased risk of cancer, digestive issues, heart problems, and mental health problems.

Can you overdose on cannabis?

It is possible to overdose on cannabis, if you take a very high dose. You may feel anxious or panicked or have a rapid heartbeat. In rare cases, an overdose can cause paranoia and hallucinations. There are no reports of people dying from just using cannabis.

Is cannabis addictive?

Cannabis can be addictive. THC levels in products have increased over time. Stronger products raise the risk of addiction, known as cannabis use disorder. You are more likely to become addicted if you use cannabis every day or started using it when you were a teenager.

When you try to quit, you may have mild withdrawal symptoms such as:

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

What is medical cannabis?

The cannabis plant contains chemicals that may help with some health problems, but it's not clear if the whole plant can treat or cure them.

Recreational cannabis is still illegal under federal law. Federal rules have eased somewhat for medical cannabis and FDA-approved cannabis drugs.

The Food and Drug Administration (FDA) has approved man-made forms of THC. These drugs treat nausea caused by chemotherapy and increase appetite in people with certain health conditions who have lost a lot of weight. There is also a liquid drug that contains CBD. It treats three forms of severe childhood epilepsy.

Researchers are studying whether cannabis and its ingredients may treat more conditions. Most U.S. states allow medical cannabis, and about half also allow recreational use for adults 21 and older.

NIH: National Institute on Drug Abuse