Our results have etiologic and clinical implications that challenge the current conceptualization of psychopathology as consisting of specific, individual psychiatric or substance use disorders. These disorders show considerable comorbidity due to shared variance at an underlying (i.e., latent) level. Clinicians may better serve patients with comorbid mood/anxiety, or substance use and impulsivity-related disorders, if their comorbidity is seen as an indication of high INT and EXT dimension levels, rather than as multiple specific disorders (Livesley, 2008; Eaton et al., 2011). Additionally, clinical interventions could focus on a cluster of symptoms and behavioral problems related to a particular dimension of psychopathology instead of using treatments tailored for one particular disorder. Further, research on the etiology of mental and substance use disorders should focus on understanding genetic and environmental predispositions towards INT and/or EXT as well as the additional specific factors that may determine how this liability is expressed for each individual (Kendler et al., 2008; Torgersen et al., 2008).
