There are several limitations to be considered. First, this represents recruitment from a single metropolitan area. Second, it is important to note that this is a case-cohort study, not a case-control study. The purpose of the community-based cohort is not necessarily to compare dependent and non-dependent individuals, but rather to compare cocaine dependent cases recruited from treatment centers with people in their own neighborhoods. Thirdly, data are not available on how many times each subject experienced a traumatic event and subsequently we cannot determine if a reported traumatic event was a single incident versus a series of events (e.g., rape vs. ongoing sexual abuse). In addition, some traumatic events, such as domestic violence, were not directly queried using the standardized assessment. Also, PTSD rates may have been underestimated, given current debate on the inclusion of criterion A in PTSD diagnoses (Kilpatrick et al., 2009). Finally, since the assessment was not designed to examine the temporal order of trauma exposure and drug use, it is unclear whether traumatic events occurred before or after the development of substance dependence. Additionally, data are not available on whether traumatic events occurred during the use of cocaine or other substances.
