After several voyages, Columbus and others introduced tobacco to Europe and it was listed as a cure for every known disease at the time. Nicotine has several important interactions with other psychotropic medications via the P450 system .
Many smokers report a sense of relaxation when they smoke a cigarette.
This isn't the cigarette. They are relieving their withdrawal symptoms. Remember that nicotine causes upregulation of acetylcholine receptors and when these aren't occupied, one feels irritable and restless.