Understanding Inertia Inherent Limitations on Evaluating “Upstream” Prevention Interventions

Intervention Strategies “Upstream” Interventions School and community based prevention Disrupting Supply “Downstream” Interventions Treatment Incarceration of Users Enforcement/Treatment Partnerships

Understanding Inertia Empirical illustration using household survey data Structural explanation with a model of illicit drug use Mathematical representation of system inertia

Empirical Illustration Source SAMDHA 2006

One Year Interruption of Initiation

One Year Interruption of Initiation

Permanent 33% Drop

Permanent 33% Drop

Two-Stage Model

Two-Stage Model

Two-Stage Model

Mathematical Representation f(t) probability that an individual manifests outcome of interest in year t I(t) Initiation in year y X(t) aggregate level of outcome at time t

Convolution Integral One year interruption of initiation with f(t)=1 for T = 0.5, T = 1, T = 2, T = 10, years.

Conclusions For upstream interventions evaluated with downstream indicators…

Conclusions For upstream interventions evaluated with downstream indicators… …No news is really no news.

Thanks!