“It appears that smokers have an altered opioid flow all the time, when compared with non-smokers.
And smoking a cigarette further alters that flow by 20 to 30 percent in regions of the brain important to emotions and craving” as explained in an WikiPedia article.
This may help us understand a link between cigarettes and desire to smoke.
Smokers enjoy their habit because it stimulates the flow of “feel good” chemicals in the brain, according to a new study involving just a handful of test subjects.