Introduction to the special issue: transitions in substance use across time, gender, and culture.

This special issue had its origins in a symposium arranged for the Ninth International Congress on Twin Studies, held in Helsinki, June 1998. The symposium consisted of six submitted or solicited papers that used twin comparisons to examine transitions in substance use and abuse across time, gender, and culture. It was well received, and before the Congress ended, plans were formulated to turn the symposium into a special issue of this journal. Five of the Congress Symposium presentations have been adapted for this issue. Four additional papers were solicited to extend the range of issues and substances surveyed and the characteristics of the twin samples employed; several of the added papers were adapted from presentations made at the Stockholm meeting of BGA, which was held the week following the Helsinki Twin Congress. It is appropriate that this special issue, directed to twin studies of substance use and abuse, had its origins in meetings in Helsinki and Stockholm. One of the first conventional comparisons of smoking habits in adult twins was reported by Stockholm investigators four decades ago; Friberg et al. (1959) reported significantly greater concordance in MZ than in DZ twin pairs in a sample of adult twins born in the early part of the century in Lund University Hospital. Seven years later, the first major twin study directed to patterns of social drinking was reported with data from a population-based cohort of adult Finnish twin brothers. Juha Partanen and his collaborators, Kettil Bruun and Touko Markkanen, published their findings as "Inheritance of Drinking Behavior," a volume in the Finnish Foundation for Alcohol Studies, dated September 1966. This three-decade-old work provides an appropriate context for analyses reported in this spe-