Profile of executive deficits in cocaine and heroin polysubstance users: common and differential effects on separate executive components.
OBJECTIVE
Structure of executive function was examined and we contrasted performance of substance dependent individuals (polysubstance users) and control participants on neuropsychological measures assessing the different executive components obtained. Additionally, we contrasted performance of polysubstance users with preference for cocaine vs heroin and controls to explore possible differential effects of the main substance abused on executive impairment.


METHODS
Two groups of participants were recruited: abstinent polysubstance users and controls. Polysubstance users were further subdivided based on their drug of choice (cocaine vs heroin). We administered to all participants a comprehensive protocol of executive measures, including tests of fluency, working memory, reasoning, inhibitory control, flexibility, and decision making.


RESULTS
Consistent with previous models, the principal component analysis showed that executive functions are organized into four separate components, three of them previously described: updating, inhibition, and shifting; and a fourth component of decision making. Abstinent polysubstance users had clinically significant impairments on measures assessing these four executive components (with effect sizes ranging from 0.5 to 2.2). Cocaine polysubstance users had more severe impairments than heroin users and controls on measures of inhibition (Stroop) and shifting (go/no go and category test). Greater severity of drug use predicted poorer performance on updating measures.


CONCLUSIONS
Executive functions can be fractionated into four relatively independent components. Chronic drug use is associated with widespread impairment of these four executive components, with cocaine use inducing more severe deficits on inhibition and shifting. These findings show both common and differential effects of two widely used drugs on different executive components.
Verdejo-García
Antonio
A
Department Personalidad, Evaluación y Tratamiento Psicológico, Universidad de Granada, Campus de Cartuja S/N, 18071, Granada, Spain. averdejo@ugr.es
Pérez-García
Miguel
M
D000328:Adult; D000437:Alcoholism / Q000150:complications / Q000523:psychology; D019969:Amphetamine-Related Disorders / Q000150:complications / Q000523:psychology; D001288:Attention / Q000187:drug effects; D016022:Case-Control Studies; D019970:Cocaine-Related Disorders / Q000150:complications / Q000523:psychology*; D003071:Cognition / Q000187:drug effects*; D003657:Decision Making; D005163:Factor Analysis, Statistical; D005260:Female; D006556:Heroin Dependence / Q000150:complications / Q000523:psychology*; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000523:psychology; D008568:Memory / Q000187:drug effects; D011237:Predictive Value of Tests; D025341:Principal Component Analysis; D012720:Severity of Illness Index; D013030:Spain; D013375:Substance Withdrawal Syndrome / Q000523:psychology*; D014705:Verbal Behavior / Q000187:drug effects