[Smoking initiation: epidemiology, research, and behavioral sciences].

Becoming a regular smoker is a process that begins even before the first cigarette, and ends in lifelong physical and psychological dependence. Various psychological and behavioral factors contribute to this process. This article discusses smoking initiation from a comprehensive perspective, including the physiological and addictive effects of nicotine, and the personal and environmental factors that lead to smoking. Because smoking usually begins in adolescence, special emphasis is placed on this developmental stage and on the situations that encourage teenagers to smoke the first cigarette. Finally, this article analyzes the importance of the initiation process in the epidemiology and prevention of smoking. This approach may prove to be particularly useful to clinicians interested in interventions aimed to curb smoking.