This article reviews recent developments in our understanding of impulsivity as they relate to brain circuitry that might underlie these comorbid factors, focusing upon the clinical features of substance use (and dependence), bipolar disorder, and pathological gambling. Individuals who are affected by these disorders exhibit problems in several domains of impulsive behavior including deficient response or "motor" control, and the tolerance of prolonged delays prior to larger rewards at the expense of smaller rewards ("delay-discounting"). These populations, like alcoholic dependents, also exhibit impairments in risky decision-making that may reflect dysfunction of monoamine and catecholamine pathways. However, several areas of uncertainty exist including the specificity of impairments acro...

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