Marijuana and Lung Cancer

Reviewed by: HU Medical Review Board | Last reviewed: January 2017.

Marijuana, also known as cannabis, is a plant that contains chemicals called cannabinoids. Some cannabinoids affect the brain, changing mood and/or consciousness. Both marijuana and cannabinoids may be addictive.1

Marijuana is often smoked; however, it also comes in ingestible or topical forms. Possession of marijuana is illegal in the United States outside of approved research settings; however, a number of states have legalized marijuana for medical purposes.1

Does Marijuana Increase the Risk of Lung Cancer?

Inhaling smoke of any kind is harmful to the lungs. A recent review was conducted of published research to assess the effects of inhaled marijuana on the lungs. The review included 48 journal articles across several countries. The data indicates that smoking marijuana increases the risk of lung cancer. In addition, the review showed smoking marijuana was associated with an increased risk of emphysema, spontaneous pneumothorax (collapsed lung), and chronic obstructive pulmonary disease (COPD).2

However, there have been other studies that do not show a correlation between marijuana and lung cancer, so the evidence is inconclusive. There have been few long-term studies on the effects of marijuana smoking, mostly due to the legality of marijuana. More research is needed to determine the definitive effects of marijuana on lung function and the risk of lung cancer.3

How is Marijuana Used Medically in Lung Cancer?

Marijuana, or cannabis, and cannabinoids have been studied in clinical trials as a method for reducing or managing side effects of cancer and cancer treatment, including:

Reducing nausea and vomiting

The Food and Drug Administration (FDA) has approved two cannabinoid drugs (dronabinol and nabilone) for the treatment of chemotherapy-related nausea and vomiting in patients who have not responded to standard therapy. Various trials have studied inhaled cannabis for reducing chemotherapy-related nausea and vomiting with mixed results. One small trial showed benefit in treating chemotherapy-related nausea and vomiting using an oral spray with delta-9-THC and cannabidiol.

Stimulating appetite

Delta-9-THC (dronabinol) was not shown to increase appetite or weight gain in patients with advanced cancer when compared to standard treatment (megestrol), although it has been shown to increase appetite in patients with HIV/AIDS compared to placebo. There are no published research studies on the effect of inhaled cannabis on appetite in cancer patients, although studies of healthy people indicate that they consume more calories.

Relieving pain

Several studies have suggested that cannabis or cannabinoids can relieve pain when inhaled or taken by mouth.

Reducing anxiety and improving mood

A small study suggested that patients who inhaled cannabis experienced improved mood, less anxiety and an improved sense of well-being.1

Common Side Effects of Marijuana

Marijuana may cause side effects including rapid heart beat, low blood pressure, muscle relaxation, bloodshot eyes, slowed digestion, dizziness, depression, hallucinations, or paranoia.1

Where is Medical Marijuana Legal?

While U.S. federal law prohibits the possession of marijuana outside approved research settings, a growing number of states have enacted laws legalizing marijuana. Medical marijuana laws vary from state to state, and currently several states have legalized medical marijuana, including Colorado, Washington, Oregon, California, Nevada, Arizona, New Mexico, Minnesota, Illinois, Michigan, Maine, New Hampshire, Vermont, New York, Massachusetts, Rhode Island, New Jersey, Connecticut, Maryland, Delaware, Alaska, Hawaii, and the District of Columbia.1

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