Substance abuse and mental illness do not occur in isolation of physical illness that may account for additional variability in adverse outcomes. TBI, for example, has been associated with elevated impulsivity, an underlying risk factor in substance use, various mental illnesses, suicidal thinking, violent interpersonal behavior, and legal problems (e.g. Olson-Madden et al., 2012). Chronic pain has similarly been linked to substance use, mental illness, and various adverse outcomes (e.g. Braden and Sullivan, 2008). In addition, the associated conditions discussed in this section are not mutually exclusive categories of risk. We suggest that future study designs control or otherwise account for the influence of various risk factors on adverse outcomes to assess the unique variance accounted for by dual diagnoses. For example, there may be a direct effect of dual diagnosis on homelessness or the relationship may be mediated through unemployment. As we have seen in the current review, many VHA data sets are substantial enough to provide adequate power when assessing complex relationships.