The current study provides strong support for the conceptualization of substance dependence as a dimensional construct, both in terms of individual substances and at a higher-order level encompassing a range of multiple substances. Factor loadings indicate that the higher-order multi-substance dependence factor explained 50–80% of the observed variance in each of the substance-specific dependence factors. The construct of multi-substance dependence has been previously and consistently shown to be an indicator of the broader externalizing spectrum, encompassing a range of substance use and misuse measures, non-substance disinhibitory behaviors (including criteria for Conduct Disorder and Antisocial Personality Disorder), personality constructs (such as impulsivity), and aggression. [42] Although there is substantial overlap between general externalizing and substance-related problems, there remains variance that is unique to substance problems. Environmental aspects may account for some of the unique variation in substance problems, including availability of specific substances or cultural influences on what is considered normative versus problematic use. [43]
