Maximum information was provided at decreasing trait levels as age increased. This can be seen in Figure 2, where the TIC peaks are located farther to the left on the Z-score scale as age increases. As age increases, endorsement rates across substances also increase, making substance use relatively more normative and moving the TIC toward a middle level of poly-substance use. This suggests that age effects are well conceptualized at the level of the underlying poly-substance use trait.
