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Is Marijuana Safe?

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WebMD Feature

Is the idea of marijuana as an illegal drug starting to go up in smoke?

Two states have already legalized pot for recreational use. And since polls show that most Americans are in favor of the practice, it might not be long before joints are rolled and bongs are smoked in many more states without fear of jail time.

Even though the laws are shifting, the debate over legalized marijuana continues. Although some say marijuana is just as safe as, or even safer than alcohol, others argue that pot causes a lot more harm than just a serious buzz.

Although there isn't much evidence that the occasional toke leads to long-term health problems, researchers are concerned that long-term, heavy pot smoking can leave lingering effects. 

"I don't think we can definitively say it is safe," says Jeanette Marie Tetrault, MD, FACP. She's an assistant professor of medicine at the Yale University School of Medicine. 

Ongoing marijuana use has been linked to lung changes, memory loss, and a number of other health problems.

Your Body on Marijuana

When you smoke pot, THC and other chemicals travel from your bloodstream to your brain. THC causes the feel-good "high."

Here are some of the other effects you'll feel:

  • Trouble thinking and remembering
  • Bloodshot eyes
  • Dry mouth (cotton mouth)
  • Increased appetite (the "munchies")
  • Fast heart rate
  • Slowed coordination

Marijuana Smoke: What's in It?

Marijuana smoke contains about 60 chemicals called cannabinoids. The best-known of these is THC, which also leads to the signs that someone has been smoking pot: the memory loss and random thoughts, as well as the unsteady walk.

Breathing In the Smoke

Marijuana smoke is also filled with many of the same chemicals as tobacco smoke, including ammonia, hydrogen cyanide, and formaldehyde. Some of these chemicals are known to cause cancer. Most users smoke pot in a joint or water pipe, so they breathe the smoke straight into their lungs.

There's no proof that smoking marijuana causes lung cancer like cigarettes do. But people who smoke pot do show signs of damage and precancerous changes in their lungs, especially if they also smoke cigarettes. And a study published in 2013 in Cancer Causes & Control found that heavy marijuana smoking might raise the risk of lung cancer.

Pot smoking leads to other lung effects, too. "We know that patients see their doctor with more symptoms, including cough and wheezing, when they're marijuana smokers," Tetrault says.

 

Marijuana on the Brain

Could smoking marijuana change the way the brain works? That's what researchers are finding.

  • Brain imaging scans of heavy marijuana smokers have revealed changes in blood flow to parts of the brain involved in memory and attention. Researchers have also noted differences in the size and shape of the thalamus, the part of the brain that's involved in consciousness and information processing.
  • Heavy pot smokers in studies score lower than non-users on tests of memory, attention, and learning. The more they smoked, the worse they did.
  • The effects of smoking pot may be even more pronounced in teenage smokers than adults, because teens' brains are still developing.
  • Regular users are more likely to be diagnosed with schizophrenia, especially when they have a family history of the condition.

Marijuana Poll

Do you think marijuana is safer than alcohol?

View Results