Using trend theory to explain heroin use trends.

Trend theory is an effort to integrate histories of populations and distribution systems to explain the key epidemiological question: why do these people in this place at this time experience a rapid increase in heroin use? The theory grew out of work on heroin trends in the Baltimore metropolitan area, specifically on epidemics among urban African-Americans in the 1960s and among suburban white youth in the 1990s. This overview represents trend theory as an instance of agent-based adaptive models characteristic of complexity theory.