The same research team investigated the genetic and environmental influences on transitions in drug use patterns that varied from experimental to occasional, regular and eventually abuse or dependence [39]. Patterns across heroin use showed that heritability estimates are about 0.50 (95% CI: 0.00-0.56) for the transition from experimental to occasional use, and about 0.01 (95% CI: 0.00-0.31) for the transition from occasional to regular use [39]. In contrast, specific environmental influences showed significant contributions to the same transitions: 0.50 (95% CI: 0.32-0.38) from experimental to occasional use of heroin, and 0.99 (95% CI: 0.62-0.99) for occasional to regular use [39].
