Indices of lifetime polydrug use among adolescents.

The functional equivalency for three indices of lifetime polydrug use was examined in a sample of adolescents (N = 794). The following indices were included in analyses: (a) a count of lifetime self-report of substances used; (b) an index weighted by the severity of the substances used; and (c) a hierarchical index of substance use. Analyses for each index was conducted twice with abstinent youth (no report of substances over their lifetime) included and excluded from analyses. Relationships between the indices with gender, age, ethnicity, and country of origin were examined. The only difference between the indices found was for ethnicity in the full sample. African Americans had higher scores on the hierarchical substance use index than Latinos or Asian/Pacific Islanders. With the exception of the relationship between the hierarchical index and ethnicity, the relationships between the other demographic variables with indices were consistent. Implications for utilizing the count or weighted index versus a hierarchical index of lifetime polydrug use are discussed.