Findings should be considered within the context of study limitations. First, data were cross-sectional; longitudinal studies are needed for conclusions regarding directionality or causality. However, age-of-onset analyses indicated that approximately 75% of participants had TE and PTSD symptoms at an earlier age than their dependence symptoms onset, and between 4–8% reported that their PTSD and dependence symptoms onset at the same age. Thus, TE/PTSD occurring prior to substance dependence is most commonly reported; however, we were unable to formally incorporate age of onset into analyses because age of dependence symptom onset was only available for those diagnosed with dependence. Future longitudinal studies should include these data to confirm temporality. Second, data were based on self-report, as are most large-sample surveys of the issues addressed above. However, the use of reliable, validated measures of psychopathology lessens such concerns. Third, for theoretical reasons and ease of interpretability, the current study focused only on how PTSD affected relations between TE and various types of SUD; however, future studies should consider whether other forms of psychopathology (e.g., depression) also account for additional portions of
