While previous studies examined the issues of age and sex differences (or similarities) in the factor structure of SUDs, there have been far fewer investigations comparing the factor structure of SUDs across multiple sampling schemes. Studies comparing the structure of non-substance characteristics between population and clinical samples found that the same factor structure applies when examining measures of intelligence [24], broad neuropsychological batteries [25], and death distress. [26] Here, clinic-based and population samples are not distinguishable by their measurement structures, but rather simply differ in their average trait levels. Conversely, a measure of alexithymia (difficulty understanding emotions) displays a slightly different factor structure when comparing clinical and volunteer samples. [27]
