The addictive nature of cigarette smoking has been appreciated only in the past two decades. Prior to the publication of DSM-III in 1980, excessive tobacco use had not been considered as a psychiatric problem requiring treatment . Smoking has been recognized as a serious medical problem since thefirst Surgeon General's Report on Smoking and Health in 1964. An important development during the 10 to 20 years following this report was the growth of knowledge regarding the physiological effects of regular tobacco use and the importance of nicotine as the main pharmacological ingredient in tobacco. This body of information culminated in the 1988 Surgeon General's Report, which recognized chronic tobacco use as a form of addictive behavior . Nicotine, like other drugs of abuse, has reinforcing psychoactive effects that lead to its repeated self-administration. Nicotine stimulates the release of several neurotransmitters including dopamine, norepinephrine, acetylcholine, 5-hydroxytryptamine, gamma-aminobutyric acid (GABA) and endorphins . Through its effects on the dopaminergic, or 'reward', system, nicotine exerts psychoactive effects such as an increased sense of enjoyment. The norepinephrinergic effects of nicotine may account for increased attentiveness and improved performance in repetitive tasks, while its anxiolytic effects are likely mediated through GABA and the endorphins.