Posttraumatic stress disorder (PTSD) and substance use disorder (SUD) are both common psychological problems and they are frequently comorbid. However, there is little longitudinal research that can disentangle their temporal relationship towards determining the mechanisms in their comorbidity. Furthermore, the extant research does not consider possible confounds to diagnosis that are relevant to the area of psychological injury and law, such as exclusion of cases of malingering after appropriate assessment and testing. This paper reviews the literature on the question of comorbidity of PTSD and SUD towards establishing preliminary conclusions that could serve directions for needed research in the area, and with potential application to individual assessment and court purposes. There are four major models in how PTSD and SUD relate-selfmedication, high risk, susceptibility, and shared vulnerability. Overall, the self-medication model is supported, but not exclusively. Recent research is examining the different models in these regards with respect to individual differences, including in negative emotionality/constraint, emotional/dysregulation, and patterns in PTSD's different clusters. Further research is required from a forensic perspective that uses the appropriate populations, rules out malingering in the cases studied, and controls other confounds applicable to the forensic context. This article examines models of the comorbidity of posttraumatic stress disorder (PTSD) and substance use disorder (SUD), concentrating on alcohol use disorder (AUD). The disorders often co-occur, and their comorbidity in cases of psychological injury presents difficulties both to assessors and attorneys involved in the cases. For example, after an event at claim in which PTSD develops, does the alcohol consumption that might ensue reflect (a) a response to the trauma and PTSD, as in self-medication to alleviate the symptoms; (b) the continuation of a pre-existing alcohol consumption, perhaps exacerbated by the trauma/PTSD; (c) an underlying psychological construct or personality trait fully unrelated to the trauma/PTSD (e.g., lack of inhibition, high-risk behavior, externalizing behavior); or (d) other possibilities, ranging from the effects of drinking and driving to a multifactorial causality with at least two if not all these factors involved, including reciprocally and in mutual maintenance and exacerbation?The article is organized into sections that first cover PTSD and AUD as presented in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; American Psychiatric Association, 2013). Then, the article considers the prevalence of PTSD/SUD (AUD) comorbidity as found in a variety of recent studies. Next, the article examines the major models on PTSD-SUD (AUD) comorbidity and the research cited in the recent publications presenting these models. Next, the article analyzes in depth the empirical research in these recent studies on the comorbidity of PTSD and SUD (AUD). For this purpose, we used a tabular...