Several lines of evidence indicate that nicotine may contribute to the development of cancer. Evidence from experimental in vitro studies on cell cultures, in vivo studies on rodents as well as studies on humans inclusive of epidemiological studies indicate that nicotine itself, independent of other tobacco constituents, may stimulate a number of effects of importance in cancer development.
Nicotine is a neuroactive substance that triggers the release of neurotransmitters such as dopamine, causing a pleasurable sensation. However, due to its actions on the brain, it also leads to nicotine dependence because, after several consumption sessions, the brain no longer functions properly. The brain constantly strives to maintain balance in the body. If nicotine artificially stimulates the release of neurotransmitters, the brain will attempt to reduce the amount of neurotransmitters it naturally produces. After a period of time, the brain becomes accustomed to nicotine and produces very little dopamine naturally. When nicotine is no longer present, the brain enters a state of depression. It takes a long time for the brain to return to its optimal level of dopamine.
The consensus amongst nootropic cognoscenti is that it can make you smarter but it also can get you started smoking/vaping/chewing. These are Pretty Bad and the risk of using tobacco/vapes isn’t worth being a little smarter.
Gwern has a writeup on it. If you really want to use it, try breaking nicotine gum into small pieces and using very sparingly.