Most research points to cigarette smoke, not nicotine, as being the primary contributor to cancer among smokers. However, although most experts agree that nicotine does not directly cause cancer, some research suggests that nicotine may lead to a type of DNA damage that increases the risk of cancer. Research from 2015 reported in the Indian Journal of Medical and Paediatric Oncology suggests that nicotine may increase the risk of cancer because it might damage DNA, initiate cancer and cause it to progress faster, and interact with cancer-causing chemicals.