In addition to frequently being comorbid with substance use disorders (SUDs), psychiatric disorders may be associated with an increased severity of these disorders (Cacciola et al., 2001; Compton et al., 2005b; Mills et al., 2007; Skinstad and Swain, 2001; Watkins et al., 2004). Further, substance dependence disorders may be associated with increased severity of anxiety disorders such as agoraphobia and PTSD (Grant et al., 2006), major depressive disorder (MDD; Kandel et al., 2001; Kessler et al., 2005; Kessler et al., 1994; Regier et al., 1990), bipolar disorder (Cassidy et al., 2001; Kessler et al., 1994; Regier et al., 1990), and Cluster B personality disorders, especially antisocial personality disorder (ASPD; Kandel et al., 2001).
