Marijuana is the most widely used illegal drug in the United States. It is a dry, shredded green/brown mix of flowers, stems, and leaves of the plant Cannabis sativa. A stronger form of marijuana called hashish (hash) looks like brown or black cakes or balls. The many street names for marijuana include pot, herb, weed, grass, Jane, reefer, dope, and ganja.

Marijuana is typically smoked in cigarettes (joints or spliffs), hollowed-out cigars (blunts), pipes (bowls), or water pipes (bongs). Some people mix it into food or brew it as a tea.

Short-Term Effects
The main active chemical in marijuana is THC (delta9tetrahydrocannabinol). When smoked, THC passes from the lungs into the bloodstream, which transports it to the brain and other organs. When it reaches the brain, THC connects with a certain type of receptor on nerve cells in areas that affect coordination, thought, memory, concentration, sensory and time perception, and pleasure. This causes the marijuana “high.”

Marijuana users can experience these short-term effects:

  • difficulty in thinking and problem solving
  • problems with memory and learning
  • loss of coordination
  • distorted perception

These effects can make activities like driving dangerous while under the influence of the drug.

Long-Term Effects
Research has found that side effects from using marijuana frequently over a long period of time include:

Changes in the brain. Marijuana can affect the areas of the brain that play a part in response to stress, motivation, and reward.
Fertility implications. Animal studies suggest that heavy users may experience disruptions in ovulation or produce less sperm. So it’s possible people who use a lot of marijuana might have difficulty having children as they get older. Studies also show that babies born to women who use marijuana when they are pregnant may be more likely to have developmental and behavioral problems.
Respiratory problems. People who smoke marijuana have more respiratory problems — such as having more mucus, a chronic cough, and bronchitis (irritated breathing passages).
Changes in blood pressure. Over time, continued use of marijuana can lead to decreased blood pressure, which may cause dizziness. It also seems to impair the body’s ability to fight off infections and some other diseases.
Emotional problems. Heavy users are more likely to report symptoms of depression than nonusers. They can also feel more anxiety, have more personality disturbances, and are at an increased risk of developing schizophrenia, a severe form of mental illness.
Other Possible Problems
In addition to the long-term and short-term side effects, you may have heard that using marijuana may lead to other drug use. Although it is not certain that marijuana is the direct cause, people who have used marijuana are eight times more likely to have used cocaine, 15 times more likely to have used heroin, and five times more likely to need treatment for substance abuse.

There are also legal aspects to marijuana use: Every state except Colorado and Washington has laws against growing, possessing, and selling marijuana. Penalties vary from state to state, but they usually involve fines and/or jail time for those caught using or distributing marijuana. People who use marijuana may end up with criminal records that can hurt plans for college or finding a job.

Speaking of jobs, more and more places test for drug use as part of the hiring process. It can take several weeks for marijuana to leave someone’s body. So people who use marijuana may find they don’t get a job they want — or, if their place of work does ongoing drug tests, they may lose their jobs.