In this study, we have compared several neuropsychological measures and social adjustment from a group of Brazilian CCDI, to a comparison (control) group matched in age, gender, education, socioeconomic level, ethnicity, handedness, as well as IQ. Despite not having found statistically significant differences between the two groups on the WCST, we found that the CCDI made more disadvantageous choices on the IGT. Thus, the CCDI demonstrated problems in learning to choose advantageously on the IGT, reflected by a certain myopia for the future consequences of their choices. In addition, it was shown using the SAS-SR that the CCDI had higher levels of social dysfunction, in several areas of the social domain, including work, leisure, family, and finances. A statistical analysis suggested that the latter two results were correlated; specifically, it indicates a negative correlation between decision making and an objective measure of social dysfunction (ie, worse decision making was associated with worse social functioning). Our data confirm the ecological validity of the IGT even in a different culture, such as the Brazilian culture.
Considering that recent studies have shown that CCDI present with signs of OFC dysfunction, and that they have strong difficulties in controlling their drug use despite rising negative consequences, it is plausible to suggest that the social maladjustment detected in these patients is associated to an underlying OFC dysfunction. In this study, it is unlikely that the social environment was the precursor of the expressed social problems of the CCDI, because these subjects were from the same geographical regions and socioeconomic and ethnic groups as the subjects of the control group. A possible explanation is that the OFC dysfunction would be a predisposing factor that may have led to the poor decision making as well as the social dysfunction among the CCDI. This dysfunction can be the by-product of an interaction between genes and the environment. For instance differences in certain serotonergic or dopaminergic circuits and gene products could influence the functional activity of the neural circuits involved in decision making. Another possible explanation is that OFC dysfunction could be induced or even exacerbated by cocaine use. In fact, recent studies suggest that chronic cocaine use induces persistent changes in gene expression with potential negative impact on synaptic functioning in the OFC.41
Therefore, cocaine-related OFC dysfunction could lead to a variety of negative social consequences, such as unemployment, legal problems, financial debts, abandonment by friends, spouse, and family members, which could, therefore, be manifested by poor scores on the SAS-SR.
The present results agree with findings of other neuropsychological studies that have demonstrated decision-making impairments and OFC dysfunction in CCDI.7–10,13,15,20
It is noteworthy that the CCDI showed decision-making deficits somewhat similar to those observed in neurological patients with OFC lesions.14
One possible explanation of such decision-making deficits is the particularly high degree of crack-cocaine dependence found among the CCDI. Another is the associated use of other substances such as tobacco and alcohol, which are also known to be harmful to decision making and the PFC.12,13,15,42,43
Considering that the WCST was designed to assess mental flexibility,30
and that addicts persist with drug use despite its adverse consequences, one might expect an excessive number of perseverative errors among the CCDI. Several studies in the literature have found deficits on the WCST among cocaine abusers.15,44–48
However, the present investigation did not find differences between CCDI and the control group in the WCST. This is consistent with several other studies that failed to detect impairment on the WCST.10,20,25,49–53
The question of why the WCST yield inconsistent results remains to be studied further. One possibility that explains the inconsistency is the type of addicts that are being tested. It is possible that patients who seek treatment voluntarily, remain in treatment, and are relatively more functional, express impairments on only more sensitive OFC tasks, such as the IGT, but not on more dorsolateral prefrontal cortex (DLPFC) tasks, such as the WCST. However, addicts with more severe problems and who are less functional are more likely to show impairments on the IGT as well as the WCST. Also, in the WCST, the subject has to make a decision immediately after the examiner's feedback, meaning that analysis of future consequences is not a prerequisite as is the case in the IGT.
The fact that there was no correlation between the IGT and SAS-SR in the control group, presumably because the subjects in this group had a good social functioning (the SAS-SR variability among the control group was very low), strongly indicates that the negative correlation of these tests in the CCDI is explained by cocaine use. Thus, this study reveals a link between decision making (IGT) and an objective measure of social dysfunction (SAS-SR) in CCDI. Also, the present study demonstrates that the IGT, and presumably other decision-making tasks that measure the same construct,54
have good ecological validity, which may be extended to developing countries and other cultures, namely Brazilian culture, since their results are associated with real-world decision making.17
We suggest that such tasks may be used as indicators, of how well the CCDI will perform in real life, after an initial detoxification and drug abstinence period.
Despite the important strengths, some limitations of this study need to be highlighted. First, the present study included a small sample size and it was unable to detect more significant interactions. However, the results are in line with our initial hypothesis. Second, our sample was limited to male individuals. Although social dysfunction and risk-taking behavior are common in both males and females addicted to cocaine,55
males do have distinct behavioral, hormonal, and neuroimaging patterns.56–58
Third, since the present data are cross-sectional, it was not possible to determine whether the cognitive impairments observed were antecedents or consequences of cocaine use.47
It is very difficult to determine to what extent the drug per se, through its influence on brain functioning, leads to behavioral alterations such as increased risk taking, decision-making impairments, and social dysfunction. The possibility that the unusual social environment of drugs users also influences behavior should also be born in mind. Controlled studies of both animals and humans have strongly suggested that cocaine use leads to OFC dysfunction.8,13,18,41
Indeed, even brief periods of exposure to cocaine use may lead to long-lasting functional and structural deficits in the OFC.18
Therefore, the argument that the OFC dysfunction may precede the crack-cocaine dependence and social dysfunction must be received with caution. We also have to consider that crack-cocaine use may induce or exacerbate OFC dysfunction and poor social functioning. Fourth, the present study was based on self-reported cocaine and other drug use, for both the CCDI and the control group. However, the CCDI were predominantly inpatients, they were under the supervision of the clinical staff, and there has been significant evidence that self-reported drug use has been shown be valid.59
Fifth, it was not possible to determine the reversibility of decision-making deficits and social maladjustment, because the abstinence period was too short. Decision-making deficits may be attenuated by abstinence,20
but other authors have found that even longer periods of abstinence (6 months to 3 years) are not sufficient to improve decision making in alcoholics.60
Although several studies show recovery in neuropsychological functioning after a period of abstinence, it appears that this recovery seems to apply only to “cold” cognitive tasks such as the WCST, but not to “hot” decision-making tasks, such as the IGT. This corroborates that poor decision making, as captured by the IGT, may represent a predisposing factor, which is brought about by either genetic factors, or early environmental factors (eg, chronic emotional stress), which may impact the normal development of the PFC, which in turn leads to poor decision making, which heightens the risk for acquiring addictive disorders and poor social function. The crack-cocaine and other drug use would have an additional negative impact on OFC functioning in these subjects, but further studies are needed to investigate the nature of this association.