The smoke from marijuana damages DNA in ways that could raise the risk of cancer, according to a new study.

Researchers at the University of Leicester based their finding on studies done in labs, not in pot smokers.

Study author Raj Singh said that previous studies have shown that tobacco smoke has more than 4,000 chemicals, including 60 carcinogens. But marijuana smoke, which hasn't been studied as much, has 400 compounds. But because it doesn't burn as well, it contains more carcinogens.

Tobacco smoke has also been shown to change DNA.

The researchers wrote that because pot smokers inhale more deeply than cigarette smokers, it may give the substances more time to damage DNA.

The results were published in the journal Chemical Research in Toxicology.