The use of the case-crossover design in studying illicit drug use

The case-crossover design was developed to study time-varying exposures tha t cause transient excess risk of acute health events. It is a variant of ca se-control and subject-as-own-control research designs, involving use of in formation about exposure history of each case to estimate the transient eff ect. This kind of self-control design can help to reduce sampling bias othe rwise introduced in the selection of controls, as well as confounding bias that might be derived from enduring individual characteristics, especially personality traits and other long-standing inherited or acquired vulnerabil ities. When the subject is used as his or her own control, these personal v ulnerabilities are matched. In this paper we discuss strengths and weakness es of the case-crossover design and suggest applications of the case-crosso ver design in epidemiologic studies on suspected hazards of illicit drug us e, and in studies of drug use and co-occurring psychiatric disturbances. We conclude that the case-crossover design call play a useful role, but it di scloses a need to secure fine-grained measurements in epidemiologic researc h on psychiatric comorbidity. As explained in the paper, we also believe th e case-crossover method may be of use to criminologists who study the drugs -crime nexus, to services researchers and clinicians who seek to understand treatment entry and compliance behavior, and to etiologists interested in polydrug use. [Translations are provided in the International Abstracts Sec tion of this issue.]