MODEL RELEASED. Cigarette smoking. Face of a woman smoking a cigarette. Tobacco contains nicotine, an addictive drug which acts as a nerve stimulant. Once it has been absorbed into the bloodstream from the lungs, nicotine promotes the release of adrenalin which helps to relieve stress. Cigarettes also contain tar and carcinogens which are a major cause of lung cancer, heart disease and chronic bronchitis.