Neuropsychological consequences of alcohol and drug abuse on different components of executive functions.

Several studies have shown alterations in different components of executive functioning in users of different drugs, including cannabis, cocaine and heroin. However, it is difficult to establish a specific association between the use of each of these drugs and executive alterations, since most drug abusers are polysubstance abusers, and alcohol is a ubiquitous confounding factor. Moreover, in order to study the association between consumption of different drugs and executive functioning, the patterns of quantity and duration of drugs used must be considered, given the association between these parameters and the executive functioning alteration degree. Based on the multicomponent approach to executive functions, the aims of the present study were: (i) to analyse the differential contribution of alcohol versus cocaine, heroin and cannabis use on executive functions performance; and (ii) to analyse the contribution made by the severity of the different drugs used (quantity and duration patterns) on these functions in a sample of polysubstance abusers that requested treatment for cannabis-, cocaine- or heroin-related problems. We administered measures of fluency, working memory, analogical reasoning, interference, cognitive flexibility, decision-making and self-regulation to two groups: 60 substance-dependent individuals (SDIs) and 30 healthy control individuals (HCIs). SDIs had significantly poorer performance than HCIs across all of the executive domains assessed. Results from hierarchical regression models showed the existence of common correlates of the use of alcohol, cannabis and cocaine on verbal fluency and decision-making; common correlates of quantity of cannabis and cocaine use on verbal working memory and analogical reasoning; common correlates of duration of cocaine and heroin use on shifting; and specific effects of duration of cocaine use on inhibition measures. These findings indicate that alcohol abuse is negatively associated with fluency and decision-making deficits, whereas the different drugs motivating treatment have both generalized and specific deleterious effects on different executive components.