Is Weed Bad for You? The Negative Health Effects of Marijuana

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Marijuana is one of the most commonly used drugs in the United States. Although legalization activists and many marijuana users believe smoking pot has no negative effects, scientific research indicates that marijuana use can cause many different health problems.

After smoking marijuana, you can start feeling its effects almost immediately. These effects can last up to three hours. In contrast, when eating marijuana-based foods, such as gummies and brownies, the effects are delayed, but usually last longer.

Brain Health

Marijuana's main psychoactive ingredient, delta-9 tetrahydrocannabinol (THC), attaches to the brain's cannabinoid receptors. These receptors connect to nerves in the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement.

Multiple studies have linked marijuana use with a higher risk of the following psychotic symptoms:

Teen marijuana use is also linked to an increased risk of depression and suicidal behavior.

Heart Health

Inhaling marijuana smoke causes your heart rate to speed up, forcing your heart to work harder. These effects—which start within 15 minutes and can last for up to three hours— increase your chance of a heart attack. In fact, research shows your risk of heart attack can increase up to fivefold within the first hour after smoking marijuana.

The chemicals in marijuana are also linked to an increased risk of heart failure and a heart rhythm disorder called atrial fibrillation. Frequent marijuana use among young people is even linked to an increased risk of stroke compared with those who don't use the drug.

Bone Health

According to a 2017 study, heavy marijuana use on a regular basis may reduce bone density. Specifically, researchers found those who used marijuana heavily (more than 5,000 times during their lifetime) had a 5% lower bone density than those who did not use marijuana at all.

This drop in bone density raises the risk of bone-related health problems, such as osteoporosis, which can increase the risk of bone fractures.

On the flip side, other studies suggest that THC, CBD, and other cannabinoids accelerate bone healing and can make bones stronger after a fracture.

Lung Health

While marijuana may be less dangerous than tobacco to lung health, the harmful effects of smoking marijuana shouldn't be ignored. Marijuana smoke contains many of the same harmful chemicals as tobacco smoke. And like tobacco, smoking marijuana, even infrequently, can cause some of the following symptoms:

  • Acute bronchitis
  • Chronic coughing
  • Increased sputum ("phlegm")
  • Shortness of breath
  • Wheezing

According to a review published in 2019, regular marijuana smoking is also associated with respiratory problems such as chronic obstructive pulmonary disease (COPD) and recurrent lung infections.


According to a review published in 2015, one study found that marijuana smokers were three times more likely to develop cancer of the head or neck than non-smokers, but that study could not be confirmed by further analysis.

Because marijuana smoke contains a number of carcinogens and three times the amount of tar found in tobacco smoke, it would seem logical to deduce that there is an increased risk of lung cancer for marijuana smokers.

However, researchers have not been able to definitively prove such a link. Even though researchers have yet to "prove" a link between smoking pot and lung cancer, further research is needed, and regular smokers may want to consider the risk in the meantime.

Marijuana Use And Pregnancy

In addition to affecting fertility, marijuana use during pregnancy can be harmful to a baby's health and cause some serious problems. Specifically, babies born to those who use marijuana are more likely to be underweight at birth and be born prematurely. Marijuana use during pregnancy can also increase the risk of stillbirth.

Studies also show that children born to mothers who use marijuana during pregnancy exhibit some problems with neurological development. These can include:

  • Hyperactivity
  • Impulsivity
  • Problems with executive function
  • Problems with sustained attention and memory

There are also risks to the pregnant mother. Marijuana use can increase the risk of anemia, confusion, and forgetfulness during pregnancy.

12 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Buddy T
Buddy T is an anonymous writer and founding member of the Online Al-Anon Outreach Committee with decades of experience writing about alcoholism.