There are two main problems with smoking cigarettes. One involves the health risks from the chemicals in them which cause cancer, emphysema, heart problems, and many other diseases. The second problem is that the main addicting chemical in cigarettes, nicotine, destroys at least three of the natural, "feel-good" brain chemicals called neurotransmitters.
Some people get more of an "upper" effect from nicotine, because artificially stimulates their inhibitory acetylcholine and serotonin receptors. And still others get both effects. Whatever the mood changes, the brain responds to the presence of artificial chemicals by making fewer natural neurotransmitters.





