Smoking addiction is caused by a dependency on nicotine and habits formed by smoking or using chewing tobacco. Tobacco use is a major cause of death from cancer, cardiovascular disease, and pulmonary disease. Cigarette smoking is also a risk factor for respiratory tract and other infections, osteoporosis, reproductive disorders, adverse postoperative events and delayed wound healing, duodenal and gastric ulcers, and diabetes. icotine dependence occurs when you need nicotine and can't stop using it. Nicotine is the chemical in tobacco that makes it hard to quit. Nicotine produces pleasing effects in your brain, but these effects are temporary. So you reach for another cigarette. The more you smoke, the more nicotine you need to feel good. When you try to stop, you experience unpleasant mental and physical changes. These are symptoms of nicotine withdrawal.