There have been reports that cannabis can actually cure cancer. These are largely unsubstantiated, and they are mostly promoted by flimsy research and results that cannot be replicated. While a cure for any kind of cancer would be astounding, there is no proof that weed is that cure. What should be asked about marijuana is whether it causes cancer in the first place.
We already know that cigarettes cause cancer, and marijuana is consumed in a similar way. It may be safe to assume many of the same effects would be taking place. But there are different ingredients in marijuana than in tobacco. That makes the negative outcomes different as well.
They do share some common cancer-causing agents, however. The most notable one of these is benzpyrene. This is a carcinogen that causes cancer in people who have a certain genetic marker. Those who don’t have the marker don't need to worry about experiencing cancer by consuming benzpyrene, so it won’t cause cancer in everyone.
Weed also exacerbates the kind of damage that alcohol and tobacco have on the lungs and liver. It greatly increases the risk of cancer in people who smoke or drink. While It may not be able to cause cancer on its own in many cases, it certainly can speed the process along.
There is no evidence to show that marijuana will cause cancer in everybody who tries it. Some studies have shown that it would, while others contradict that. The information is too sparse and inconclusive to say for certain if weed is the cause of cancer for those who are using it. Further research needs to be done, but as it stands right now, the majority scientific opinion is that there is an increased risk for cancer with marijuana involved.
Now there are many different kinds of cancer, so it would take numerous studies to test for them all. What we do know is that marijuana, when smoked, negatively affects numerous parts of the body, particularly lung health and mental health. Even if it does not cause cancer, it is still dangerous and should be avoided by anyone who is concerned about their health.
It may be that future studies will shed more light on the question of carcinogens in weed. It may also be that those studies will show that the herb is harmless when it comes to cancer causes.
One thing that muddies the waters of research is that many people who smoke weed also tend to smoke tobacco. We already know that tobacco causes cancer without many of its ingredients, but it can be difficult to differentiate between the effects the two substances are having on the person. It is hard to find a sizeable group to study who only smoke cannabis and would be ideal research subjects for illustrating what cancer effects the cannabis has on them.
Until that research has been done, anybody who smokes weed should do so with caution.