Individuals who smoke and drink heavily are 38 times more likely to develop oropharyngeal (mouth-throat) cancer. By comparison, those who just drink have 6 times the risk, those who just smoke, 7 times. The risk of combination of nicotine and alcohol is closer to being multiplicative than merely additive.

One clue lies in studies showing that long-term alcohol consumption increases levels of cytochrome P450, a metabolic enzyme responsible for converting the tar in cigarettes to cancer-causing chemicals. Nicotine can also mitigate alcohol-related motor and coordination difficulties-hence the drinker who lights up to “steady his nerves.” Nicotine can help counteract alcohol-induced memory impairment by normalizing levels of vasopressin which are neurochemical messenger.

Alcohol, a depressant, mitigates some of the adverse effects smokers’ experience, such as an increased heart rate. And alcohol activates nicotine metabolizing enzymes, which makes it necessary to consume more tobacco to achieve the accustomed effect.

Psychological effects of nicotine and alcohol using
Both drinking and smoking are addicted. But if you try to quit smoking then you drop into nicotine withdrawal. Maybe a drink will actually help them out initially, but then they consume more and they develop even worse learning deficits, so now they begin smoking again and they end up relapsing.

This could has effect when initially nicotine and alcohol each block the adverse effects of the other. But as that happens then smokers and drinkers develop tolerance and consume greater amounts of each drug, and then when they try quitting one or the other, they then have this cognitive deficit and may reach for either alcohol or nicotine or both to try and reverse it, but they just spiral into the addiction again.