Utilizing IRT models to investigate adult lifetime poly-substance use, Kirisci and colleagues (2002) found significant differences in substance location and discrimination between males and females for each of ten substances. Though the relative rank ordering of substances’ locations remained the same between sexes (e.g., alcohol use indicated the lowest trait level, though tobacco use was not modeled), individual substances indicated higher trait levels for females than for males, regardless of the substance. Additionally, all substances provided greater information for males than females. These findings support the presence of a general poly-substance use dimension that differs by sex in adults, but do not speak to the structure of poly-substance use in adolescence, or the potential impact of age and sex on that dimension during that period. Because experimentation with substances typically develops during adolescence, understanding the nature of poly-substance use around this time would be a useful extension.
