If you are a long term smoker and have ever tried quitting for even a short period, you most likely would have noticed an alteration in your bowel habits. It is a common complaint among smokers who quit cigarettes in that they become constipated. Often it is not constipation in the medical sense. Rather it is a slight alteration of bowel habit from the norm where you pass stool less frequently or less easily than you did when you were smoking.
In fact, it is more likely to occur if you had the habit of smoking while on the toilet or just before going in for a bowel movement. So is it just your mind playing tricks on your body? While there is a psychological component to alterations in bowel habit after quitting cigarettes, there is also a physiological explanation for it.