To our knowledge, this is the first study to identify specific domains of neurocognitive performance as prospective predictors of TNC in BPD. WIT was predicted by better EC (Trails B) and visual memory (Benton) performance. By contrast, other neuropsychological domains (i.e. impulse control, working memory, attention and general IQ) were not predictive TNC.
EC in BPD has been proposed as an impaired modulatory system that impacts affective, cognitive and interpersonal domains of symptomatology [14
]. Our findings extend this line of research and suggest that behavioral coordination and modulation during the treatment process are largely based on the deployment of EC, rather than on processes of attention, working memory or behavioral inhibition. In particular, in the present study, only one of two EC tasks, Trails B, predicted WIT. A difference between the two EC tasks (WCST and Trails B) is that the Trails B emphasizes both speed and accuracy, whereas the WCST only assesses accuracy. We speculate that the combination of speed and accuracy are jointly important for treatment completion in BPD.
The capacity to flexibly and efficiently apply cognitive rules to novel stimuli may be an important prerequisite for psychosocial interventions, which demand applying new skills and insights to real world situations. Supporting these assertions, the present finding is in line with several prospective studies of alcoholism and other substance use disorders in which Trails B was predictive of participation in aftercare sessions and length of hospital stay during inpatient treatment [36
]. Our negative finding on the WCST is consistent with a study which found that WCST scores did not differ between treatment completers and dropouts in the treatment of cocaine dependence [18
In the present study, visual memory performance was the strongest neuropsychological predictor of WIT. Although there are a growing number of studies indicating that memory dysfunction predicts general outcomes of treatment in clinical disorders (e.g., schizophrenia, anxiety disorders and substance use disorders), memory performance has rarely been examined as a predictor of treatment completion. A study of cocaine dependence reported a relationship between better memory performance and treatment completion in outpatients receiving cognitive-behavioral therapy [18
]. Another recent study suggests that poorer verbal memory limits the response to cognitive-behavioral therapy for schizophrenia [38
]. Given that memory and learning are interdependent processes, the findings of the present study may point to a synergistic relationship between memory and EC performance in the effective treatment of BPD.
It is worth noting that once depression severity is accounted for in the GLM model, a significant relationship emerges between better memory and more WIT. This finding suggests that severity of depression obscures the importance of memory performance in the prediction of TNC, perhaps because depression can itself impair memory performance [39
The strengths of this study include the randomization of patients to manualized psychotherapeutic and controlled psychopharmacologic treatment conditions. Other assets of this study are the prospective nature of the predictions, the medication-free status of the patients and the comprehensive nature of neuropsychological assessment. The limits of this study include the relatively small sample and the potential for type II errors in the number of statistical tests. However, the hierarchical nature of our data analysis reduced the chance of such errors.
Treatment developers need to enhance the role of TNC prevention either as part of existing treatments, or as an independent preparatory phase of intervention prior to initiation of other therapies [40
]. Future research also needs to address the impact of neuropsychological functions and TNC on symptomatic and functional outcomes longitudinally [41