Cannabis and cancer: are they connected?

Does smoking cannabis increase your risk of cancer?

It is possible that cannabis can increase cancer risk. Why? Cannabis smoke contains many of the same cancer-causing substances as tobacco smoke. And people who smoke cannabis tend to inhale more smoke per puff and hold it in their lungs for longer than people who smoke tobacco cigarettes.

We need more evidence to know for sure if cannabis is a cancer risk. Some studies suggest that using cannabis over a long period of time may increase the risk of cancer, particularly cancers of the lung, head and neck. However, the quality of this research is not as strong as the evidence on tobacco and cancer. Other studies do not show an increased risk of cancer after long-term cannabis smoking.

The fact that many people who smoke cannabis also smoke tobacco or mix the cannabis with tobacco makes it harder to know whether cannabis causes cancer. And because there is no standard amount of THC (the main active ingredient in cannabis) in every cannabis cigarette, it’s hard to compare results across different studies.

Our perspective

There are limits to the current evidence, but we are concerned that long-term cannabis smoking may raise your risk of cancer. More research should be conducted to better understand the cancer risks associated with long-term smoking of cannabis and of exposure to second-hand cannabis smoke.