While the clinical implications of concomitant alcohol and drug problems are well established, few studies have prospectively evaluated how the correlates of AUDs and SUDs relate to combined diagnoses, and most focus on a limited number of earlier life characteristics. Cross-sectional and retrospective reports also make it difficult to disentangle whether the more severe clinical course (e.g., more intense substance use and related problems) for combined AUDs and SUDs is the consequence of concomitant substance-related syndromes or reflects a unique pattern of preexisting conditions that enhances both the risk for multiple types of substance problems and greater life impairment. No study has evaluated whether characteristics linked to combined substance-related conditions remain robust if the studied population is at high risk for one type of substance diagnosis (e.g., AUDs) but not the other (e.g., SUDs).
