“…These factors are affected by health delivery system structural characteristics as well as population characteristics (Aday et al, 1998) that include (a) social determinants that define available technology/therapeutic models for treating particular conditions as well as social norms for seeking treatment for that condition, (b) how health care is organized to meet individual service needs and relative effectiveness, and (c) individual sociodemographic and behavioral characteristics. Such health services models have been useful in analyzing the social determinants and individual characteristics of drug users that affect health service access such as co-morbidities and health beliefs (McBride, Van Buren, Terry, & Goldstein, 2000). In addition, the model has shown itself to be useful in understanding how health services organization facilitates or hinders access to needed services for drug users (McCoy, Messiah, & Zhao, 2002).…”