observed functioning at the level of the overall poly-substance dimension in the peaks of the TICs (see Figure 2), which moved toward a more central trait level as age increased. This shows that diversity of substances used provides information on lower trait levels as age increases, regardless of the specific substance or respondent sex (i.e., with increasing age, substance involvement becomes more normative). Significant information was obtained from diversity of substances used in both males and females at ages 14 and 17, indicating that even a simple measure of substance use does a reasonable job of capturing information on substance involvement throughout mid- to late-adolescence, so long as it includes multiple substances.
