Nicotine is probably safe for most people. It causes a temporary increase in heart rate and high blood pressure because it constricts the blood vessels when it’s absorbed by the body. That probably makes vaping — or any nicotine use — a poor choice for people with serious heart disease. As discussed above, it’s probably best for pregnant women to avoid too. But years of study on NRT and Swedish snus users shows that nicotine without combustion poses no discernable risk for adverse heart events or stroke.
Many people, including some doctors, have the mistaken idea that nicotine causes cancer. That is simply not true. While there is some evidence that nicotine may promote the growth of some tumors, there is none that nicotine itself causes cancer.
Current thinking is that nicotine by itself is at best mildly addictive.
Nicotine may be addictive, although there is a lot of doubt about that. Smokers get a freebase blast of nicotine to the brain, combined with other substances that increase nic’s addictive potential. Other forms of consumption, like NRT or smokeless tobacco, release the drug slowly into the body.
Current thinking is that nicotine by itself is at best mildly addictive. There is no reason to think that nicotine in e-cigarettes is any more addictive than nicotine patches or gum. According to Jean-Francois Etter and Thomas Eissenberg, “E-cigarettes may be as or less addictive than nicotine gums, which themselves are not very addictive.”