Scientists are not sure if smoking weed can cause lung cancer. However, cannabis smoke contains many of the same chemicals as tobacco smoke, which doctors know can cause lung cancer.

Additionally, many people use both cannabis and tobacco. As people who smoke tobacco are 15–30 times more likely to develop or die from lung cancer than those who do not, mixing cannabis with tobacco use will impact a person’s risk.

In this article, we will look in more detail at whether you can get lung cancer from smoking weed. We will also look at the other ways cannabis may affect the lungs and discuss the safest methods for using it.

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Researchers are not sure if smoking weed can cause lung cancer. However, there are similarities between tobacco smoke and cannabis smoke. This may mean that smoking cannabis contributes to a person’s lung cancer risk.

Smoking any product is harmful to the lungs. When plants burn, they release chemicals that can cause cancer. These are known as carcinogens.

When people inhale carcinogens, it damages cell DNA in the nose, mouth, esophagus, and lungs. Over time, this raises the risk that cells will grow in abnormal ways and form a tumor.

Tobacco smoke is linked to 80–90% of lung cancer deaths in the United States. Cannabis smoke contains many of the same toxins. In fact, compared with the carcinogens in cigarette smoke, cannabis smoke contains:

  • about 50% more benzopyrene
  • about 75% more benzanthracene
  • more phenols, vinyl chlorides, nitrosamines, and reactive oxygen species

Because people inhale more deeply when smoking cannabis, it also leads to four times the amount of tar deposits in the lungs compared to cigarettes.

However, people use tobacco and cannabis in different ways, which may affect cannabis smoke’s impact on lung cancer risk. For example, people may smoke cannabis less often than people typically smoke tobacco, as its effects last longer than nicotine.

It can also be challenging to determine whether cannabis or tobacco is responsible for lung cancer, as people often use both. Overall, scientists need to perform more studies to assess the risk.

Cannabis smoke can harm the lungs in several ways. According to the National Institute on Drug Abuse, cannabis smoke affects people by:

  • irritating the throat and lungs
  • increasing inflammation, or swelling, in the airways
  • increasing airway resistance, creating less room for air to move in and out
  • leading to hyperinflation, which occurs when air gets trapped inside the lungs, making it more difficult for the body to pull in fresh air
  • damaging or scarring small blood vessels in the lungs

According to the Centers for Disease Control and Prevention (CDC), regularly smoking cannabis also increases the risk of respiratory side effects, such as:

  • coughing
  • wheezing
  • overproduction of phlegm

Some studies indicate that smoking cannabis may cause or worsen other lung conditions. These include:


Bronchitis occurs when the airways swell. The symptoms include coughing, wheezing, and shortness of breath.

According to the American Lung Association, people who regularly smoke cannabis may be more at risk for acute bronchitis. Over time, lung damage may lead to chronic bronchitis.


Pneumonia is the result of a severe lung infection. It can be caused by viruses, bacteria, or fungi.

The tetrahydrocannabinol (THC) in cannabis can suppress the immune system, which some scientists suggest may put cannabis smokers at risk for respiratory infections, such as pneumonia.

However, studies on this have mixed results. Some find no connection between cannabis use and pneumonia.

The symptoms of pneumonia include:

  • a cough that produces green, yellow, or bloody mucus
  • fever
  • sweating
  • chills
  • shortness of breath
  • shallow breathing
  • sharp chest pain that worsens when breathing deeply or coughing
  • fatigue
  • feeling sick
  • confusion

Chronic obstructive pulmonary disease

Smoking cannabis with tobacco can contribute to the development of chronic obstructive pulmonary disease (COPD). COPD is a chronic condition that gets worse over time. There is no cure.

Symptoms include:

  • coughing or wheezing
  • overproduction of phlegm
  • shortness of breath
  • difficulty taking a deep breath

As with cannabis smoke a person directly inhales, secondhand cannabis smoke contains many of the same carcinogens as tobacco smoke. This means it may cause harm to others in a household who are exposed to the smoke.

Secondhand cannabis smoke also contains THC. This means that people can experience a “high” from inhaling it. Exposure to THC from a young age may impact brain development, causing problems with attention and memory.

Smoking is not the only way to use cannabis. Some people choose to vape, dab, or consume edibles, for example.

However, it is worth noting that many of these methods are relatively new. As a result, scientists have not yet studied their health effects in depth.


Vaping cannabis involves using a device, such as a vape pen, to heat and vaporize oils contained in cannabis. This eliminates the need for smoke.

However, there is not enough evidence to prove that vaping cannabis is safe. This method may have similar risks to electronic cigarette use.

The Food and Drug Administration (FDA) has reported hundreds of cases of serious illness and several deaths that are linked with vaping. Many of the products included THC, nicotine, or a mixture of both. Currently, it is not clear which compound causes these illnesses.


Dabbing involves inhaling a concentrated dose of THC through a dab rig, which is a type of vaporizer.

Many people believe this is safer than smoking or vaping. However, the American Lung Association says dabbing may also lead to respiratory problems.


Edibles such as candies, gummies, and beverages have become a popular way to use cannabis. They eliminate the need to inhale smoke or other substances, making edibles safer for the lungs than smoking or vaping.

However, there are downsides to using edibles. Compared to smoking, they:

  • take longer to work
  • can be difficult to control in terms of potency
  • last longer in the body

This means that if a person experiences side effects from using cannabis, they may be more severe or last longer than the side effects of smoking it. A person may also accidentally take too much.

In high doses, cannabis may cause:

It is not clear if there is an entirely safe way to use cannabis. Because many alternatives to smoking are new, doctors do not know much about their long-term effects.

Some states in the U.S. have legalized the use of cannabis on medical grounds. One of the most common uses is to treat the pain and nausea associated with cancer or chemotherapy.

In cases where there is a medical benefit to using cannabis, people can work with a doctor to weigh the risks against the potential benefits.

Scientists cannot be sure if smoking weed causes lung cancer. What they do know is that cannabis smoke contains many of the same cancer-causing chemicals as tobacco smoke. As a result, there may be some risks.

Smoking cannabis can irritate the throat and lungs and may contribute to lung conditions such as bronchitis, pneumonia, and COPD. Other methods of using cannabis, such as vaping and edibles, may be safer than smoking. However, their long-term impact is still unknown.