The drug use index: a measure of the extent of polydrug usage.

A drug use index (DUI) is constructed from actual usage data of 1,121 respondents (517 males and 604 females). It is proposed that this index represents a quantitative measure of the degree of involvement in polydrug use. Correlations between the DUI and use of 19 drugs or drug classes are reported. Furthermore, some applications of the DUI are demonstrated with specific reference to four psycho-personality tests.