People diagnosed with various mental illnesses (including schizophrenia, bipolar, depression) are significantly more likely to smoke cigarettes, and it appears that nicotine helps many/most of them cope with their illness (also called self medication).
But since cigarettes are the most hazardous nicotine delivery devices, these folks would truly benefit from switching to smokefree tobacco/nicotine alternatives.
Unfortunately, most anti tobacco activists not only believe (but insist) that the only health benefit of nicotine is as a temporary smoking cessation aid (i.e. NRT). That is also why most anti tobacco activists want all smokers (including those with mental illnesses) to quit all tobacco/nicotine usage.
It bothers me when I see statements made (even by folks who support the concept of tobaccoharm reduction) that scientists all agree that the healthiest thing that smokers could possibly do is to give up all nicotine. It isn't true. All me to repeat that:
It isn't true.
Becoming depressed, anxious, and confused is not healthy -- not for me, not for anyone. But because of the dichotemy between mind and body, the scientists and medical folks convince themselves that these so-called mental afflictions are still better for us than "being addicted." Scientists also ignore the clearly physical results of becoming abstinent from nicotine. The disease-state of high blood pressure (medical name = "hypertension") occurs in a higher percentage of "total quitters" than it does in continuing smokers. I know that statement is sacreligious, but if you go searching through Pub Med, yoiu will find the research that supports what I am saying. The best example of this is the MRFIT trials.
Scientists were trying to come up with a routine to prevent diabetes. So they came up with a couple of arms of intervention. They included dietary changes, exercise, and smoking cessation (read "nicotine cessation). To their utter surprise, they found that their intervention worked well with non-smokers. It failed miserably with smokers who actually achieved cessation. First they developed hypertension. They were given the standard starter treatment which is a medication to lower the amount of fluid in tissues ("diuretic"). The most effective of these is hydrochlorothiazide. Hydrochlorothiazide has a side effect: raising blood sugar. The result was that the smokers who quit developed diabetes at a faster rate than continuing smokers.
Then there is the weight gain. Everybody is screaming about obesity becoming epidemic, but nobody is running the numbers to see what the correlation is between nicotine cessation and weight gain large enough to achieve the medical label of "overweight" or "obese."
So I wish fervently that tobacco harm reduction experts would stop bringing up the (incorrect) idea that nicotine cessation is somehow healthier than avoiding hypertension, obesity, and "mental illness." Even those who did not have any underlying mental conditions to keep under control with nicotine suffer from negative physical effects when they stop using nicotine.
A couple of abstracts on the subject:
http://www.ncbi.nlm.nih.gov/pubmed/15569872
http://www.ncbi.nlm.nih.gov/pubmed/9099400
http://www.ncbi.nlm.nih.gov/pubmed/15738450