INTRODUCTION

Substance use and misuse present major public health problems for essentially all societies worldwide. The World Health Organization (WHO) reports that alcohol causes 1.8 million deaths yearly. Illness related to tobacco addiction causes four million deaths per year worldwide and represents the single largest preventable cause of death. In addition to health consequences, the economic and societal costs related to alcohol abuse and nicotine dependence are substantial, underscoring the importance of research devoted to understanding the development of substance use and abuse.

The initiation of alcohol and cigarette use most frequently occurs at some point in adolescence, although there is considerable variability in when people initiate. Adolescence is an intense developmental period, involving both physical and hormonal changes as well as myriad psychological and cognitive changes, all accompanied by changes in social roles and environments. These transitions are embedded in a sociocultural context; an individual's community, historical period, and culture all influence the experience and impact of adolescence. In addition, individual characteristics such as gender, coping resources, and personality all influence developmental outcomes. Whether an adolescent engages in normative or highrisk behavior can depend on a complex interplay of these individual and environmental factors. Accordingly, longitudinal research is necessary to study individual differences in paths of development, from childhood through adolescence to adulthood. It also allows prospective identification of precursors to the early initiation of substance use and the development of risky patterns of use.