Understanding Bulimia Nervosa from a neuropsychological perspective: Impulsivity and binge-purge behavior in adolescent and young adult women

Abstract

According to the biopsychosocial model of bulimia, neurobiological mechanisms called endophenotypes cause eating disordered behavior. Impulsivity has been identified as a possible endophenotype for bulimia nervosa, and individuals with bulimia who present with multiple forms of impulsive behavior are known to have worse prognoses. Executive dysfunction in impulse control purportedly manifests as behavioral under-regulation in binge-purge episodes. Neuropsychological assessments were used to analyze the relationship between impulsivity and symptoms of bulimia. Twenty-eight inpatient adolescent and young adult women with bulimia completed the D-KEFS Color Word Task, which is a version of the Stroop that contains four trials including the classic Stroop and a switching Stroop, as well as the age appropriate versions of the BRIEF rating scale and a Type-T Survey of thrill-seeking. Performance on these measures was correlated with measures of bulimia symptoms, including the EDI-3, EDE-Q, and variables of illness severity. Delay of gratification was assessed by offering subjects a choice of compensation that was either immediate and smaller or delayed and larger. Mixed results were found. The sample did not differ from the D-KEFS normative sample on total number of errors or on speed of task completion for the switching Stroop, and the sample demonstrated faster performance than the normative sample on the classic Stroop. However, a tendency to favor speed over accuracy of performance was identified. On the BRIEF rating scales, the sample self-reported significantly higher rates of executive dysfunction compared to the normative data. Additionally, some variables of impulsivity, including greater frequency of errors on cognitive tasks and self-reported deficits of executive functioning, were significantly correlated with variables of bulimia symptom severity, including self-reported bulimia symptomatology on the EDI-3 and frequency of bingeing and purgeing. Risk-taking was also found to be correlated with symptoms of bulimia. Differences were found between subjects who chose the immediate prize versus those who chose the delayed prize, including differences in cognitive task performance and symptom severity. Differences were also found for subjects with a comorbid disorder of impulse control, including bipolar disorders and substance abuse. In conclusion, a unilateral deficit of impulse control was not found to be characteristic of this sample; however, a multi-impulsive cohort was identified as having deficits of cognitive impulse control.