Lung cancer and violence are two different things.

Lung cancer is a carefully defined disease that has a few medically proven causes. One of them is carcinogens, which are present in cigarettes.

Comparing this to an action with hundreds of different possible psychological responses varying from person to person does not prove anything. There is no medically proven cause of violence. There are people who have medical conditions which can cause violence, such as adrenaline imbalance, but you will agree that is not usually the case.