The Primacy of Cognition in the Manifestations of Substance Use Disorders

Drug addiction is a serious public healthproblem that consists of a compulsivedrive to take drugs despite repeated severeadverse consequences (1). Factors thatinfluence the development and mainte-nance of addiction include access to drugs,socialenvironment,geneticpredisposition,and psychiatric comorbidities (2). Even inthe absence of specific psychiatric diag-noses, certain psychological vulnerabili-ties may serve as substrates compound-ing the initiation of drug use and thedevelopment of substance use disorders.For example,individual who are sensation-seekers, impulsive, or behavioral disinhib-ited appear more prone to develop addic-tion to both licit and illicit substances (3–6). In this context, it is to be noted that notall individuals who try these drugs becomeaddicted as about only 20% of people whohave tried drugs become addicts (7). It isalso worth mentioning that repeated expo-sure to moderate to large doses of someof these illicit drugs may be associatedwith well-known neuropathological con-sequences (8, 9) that might not be eithernecessary or sufficient for the developmentand the maintenance of addicted states.The accumulated evidence supports theview that a large number of substanceusers suffer from significant neuropsy-chological impairments (10). Neuroimag-ing studies in drug-dependent individu-als have also documented significant func-tional and structural alterations in severalbrain regions (1). These regions includemesocortical, mesolimbic, and mesostri-atal brain regions that are known to beimpacted by administration of licit andillicit drugs in both clinical and preclinicalstudies (2). In what follows, we discuss thepotential impact of illicit drugs on thesebrain regions and the associated cogni-tive consequences of these drugs. We thensuggest that these cognitive consequencesplay primary roles in the maintenance ofaddiction across several classes of abusedsubstances.