The Primacy of Cognition in the Manifestations of Substance Use Disorders

INTRODUCTION Drug addiction is a serious public health problem that consists of a compulsive drive to take drugs despite repeated severe adverse consequences (1). Factors that influence the development and maintenance of addiction include access to drugs, social environment, genetic predisposition, and psychiatric comorbidities (2). Even in the absence of specific psychiatric diagnoses, certain psychological vulnerabilities may serve as substrates compounding the initiation of drug use and the development of substance use disorders. For example, individual who are sensationseekers, impulsive, or behavioral disinhibited appear more prone to develop addiction to both licit and illicit substances (3– 6). In this context, it is to be noted that not all individuals who try these drugs become addicted as about only 20% of people who have tried drugs become addicts (7). It is also worth mentioning that repeated exposure to moderate to large doses of some of these illicit drugs may be associated with well-known neuropathological consequences (8, 9) that might not be either necessary or sufficient for the development and the maintenance of addicted states. The accumulated evidence supports the view that a large number of substance users suffer from significant neuropsychological impairments (10). Neuroimaging studies in drug-dependent individuals have also documented significant functional and structural alterations in several brain regions (1). These regions include mesocortical, mesolimbic, and mesostriatal brain regions that are known to be impacted by administration of licit and illicit drugs in both clinical and preclinical studies (2). In what follows, we discuss the potential impact of illicit drugs on these brain regions and the associated cognitive consequences of these drugs. We then suggest that these cognitive consequences play primary roles in the maintenance of addiction across several classes of abused substances.