**5. Limitations and future directions**

First, it is important to note that no formal examination of the study quality of the included literature was completed, as this step is not typical for scoping reviews [27]. It should also be noted that our choice to include unpublished theses and dissertations in the present review may have led to the inclusion of some studies with poor methodological quality, although it does help ensure that our conclusions are not hampered by publication bias.

To further assess the studies included in the present scoping review, we recommend a formal analysis of methodological quality be completed in the future to better understand how methodological variations in cue-reactivity may influence relevant outcomes. Additionally, the use of cue-reactivity paradigms as secondary outcomes in the context of behavioral and pharmacological intervention trials is an interesting research direction that should be studied further, as this may lead to important implications for understanding the breadth of response to the use of psychotherapeutic or pharmacological interventions in this population, and may point to potential mechanisms of action. We also recommend that a formal systematic review and metaanalysis be conducted to quantify the magnitude of trauma cue-induced craving responses in this population, and to identify significant moderators of this response in terms of sample characteristics (e.g., percentage of the sample with PTSD), and methodological variables (e.g., personalized vs. standardized cues). Providing that relevant data could be obtained from published papers or authors, novel techniques, such as two-step meta-analytic structural equation modeling (TS-MASEM; [68]) could also be employed to examine theorized mediational pathways (e.g., that trauma cue exposure leads to activation of negative affect which in turn activates craving). Finally, meta-analyses could also quantify the degree of reduction in trauma cueinduced craving that is achieved with various forms of treatment for PTSD, SUD, and their comorbidity, and its relations to treatment efficacy (i.e., symptom reduction).
