We also note that the current findings refer to lifetime history of substance use and dependence symptoms and so may not generalize to models of recent substance problems, where co-morbidity among substances or even symptoms within a substance may be reduced. Although we include the ever use criterion as a broad indicator of whether or not an individual has tried a substance, there remains a gap in information available in the current study between ever use of a substance and the development of dependence symptoms. Further, there are likely additional key aspects of addiction, such as treatment-relevant factors like social support, that the DSM-IV dependence criteria do not capture.
