Comorbid alcohol and substance use disorders (i.e., polysubstance use disorder: PSUD) have also been associated with brain morphological abnormalities. Liu and colleagues reported smaller normalized gray matter (GM) and white matter (WM) volumes of the prefrontal lobe in polysubstance abusers (cocaine, alcohol, heroin, marijuana) abstinent from substance use for more than 2 weeks compared to controls (Liu et al., 1998). Tanabe and colleagues also reported smaller GM volumes of the bilateral medial orbitofrontal cortex in long-term (over 2 years) abstinent individuals dependent on two or more substances (most often cocaine, amphetamine, and alcohol) compared to controls (Tanabe et al., 2009). As in AUD, the neurobiological abnormalities in individuals with PSUD are accompanied by cognitive deficiencies, particularly in visual and verbal memory, attention, psychomotor speed, visuomotor skills, problem solving and abstraction abilities (Block et al., 2002; Medina et al., 2004).
