Onset and progression of drug use in the general population of Catalonia, Spain.

The aim of the present study was to retrospectively study the onset and progression sequence of the most frequent pathways of drug use initiation in a sample of the Spanish general population. Data come from the 2011 household survey on drug use in Catalonia, Spain, on non-institutionalized individuals aged 15-64 in the general population. The final sample was of 2,069 individuals and had the same age distribution as the general population. Progressions of drug initiation were pictured by quantifying transitions from a previous state in terms of the number of individuals and weighted percentages. Survival analyses were employed to assess the most prevalent pathways found in the descriptive analysis using additive regression models. Median ages of onset were decreasing in every cohort from 1965 to 1985-1996: from 17 to 15 in tobacco, 20 to 16 in cannabis and 21 to 18 in cocaine. In people who consumed the three drugs studied, the most frequent pathway was "tobacco-daily tobacco-cannabis-cocaine". These results demand health policies and prevention strategies in order to increase perception of the risks of legal and illegal substances. This, together with well-designed peer interventions could reduce the risk of exposure to illegal drugs such as cannabis and cocaine, thus reducing the likelihood of future problem drug use.