Effects of transcranial direct current stimulation on cognitive flexibility, impulsivity and eating behavior in bulimia nervosa and binge eating disorder

Aim: Cognitive functions, impulsivity and characteristics of eating behavior in bulimia nervosa (BN) and binge eating disorder (BED) and their response to transcranial direct current stimulation (tDAU) are among the topics that have been the focus of attention recently. However, studies on this subject report conflicting results. Therefore, this study aimed to evaluate cognitive flexibility, impulsivity and eating behavior in patients diagnosed with BN and BED, and to examine their changes with tDAU applied to the dorsolateral prefrontal cortex (DLPFC). Materials and Methods: A total of 21 participants, 6 diagnosed with BN and 15 with BED, were included in this study. In the first evaluation, after the sociodemographic information of the participants was obtained, Hamilton Depression Rating Scale (HDRS), Hamilton Anxiety Rating Scale (HARS), State-Trait Anxiety Inventory-1 (STAI-1), Eating Disorder Examination Questionnaire (EDE-Q), Eating Attitude Test (EAT), Eating Behavior Follow-up Form (EBFF), BARRATT Impulsiveness Scale-11 (BIS-11), Cognitive Flexibility Inventory (CFI), Trail Making Test A and B (TMT A-B) and Modified Balloon Analog Risk Task (M-BART) were applied. Then, tDAU was applied to the DLPFC of the participants, three times a week every other day for 3 weeks, for a total of 9 sessions, and each tDAU session lasted 20 minutes. Participants received 3 sessions of right anodal left cathodal sham tDAU in the first week, 3 sessions of right anodal left cathodal active tDAU in the second week, and 3 sessions of left anodal right cathodal active tDAU in the third week, respectively. After the last application each week, the participants were re-administered HDRS, HARS, STAI-1, TMT A-B and M-BART, and the participants were asked to fill out EBFF once a day for the following 2 days, 6 times in total. Data collected from the participants four times were analyzed with repeated measures ANOVA or Friedman test. Results: Risk-taking behavior, assessed by M-BART, was found to be higher with both right anodal left cathodal and left anodal right cathodal DLPFC active tDAU. It was found that the TMT B-A score, which was applied to evaluate cognitive flexibility, was significantly lower only with left anodal right cathodal DLPFC active tDAU. The desire to eat was lower after sham stimulation and both active tDAU compared to the first evaluation; however, no significant difference was found between sham and active stimulation. The number of eating attacks was found to be lower after sham stimulation and both active tDAUs compared to the first evaluation, and was also significantly lower after active tDAUs compared to sham stimulation. On the other hand, it was observed that the anxiety level assessed by HARS was lower in all tDAUs compared to the first assessment, but there was no significant difference between sham and active conditions. Depression levels assessed by HDRS were found to be lower with all tDAUs compared to the first evaluation, and were also lower after left anodal right cathodal active tDAU compared to sham stimulation. Conclusion: The findings of this study show that both active tDAU applied to the DLPFC increase the level of impulsivity, whereas only left anodal right cathodal tDAU has a positive effect on cognitive flexibility. In terms of desire to eat, no significant difference was found between tDAU conditions, but in terms of eating attack, both active tDAUs were found to be more effective than sham stimulation. In conclusion, tDAU in eating disorders appears to be an intervention method that may have an impact on areas such as depressive symptoms and cognitive flexibility, which may affect the course of the disease, in addition to the basic symptoms. In order to understand the effects of tDAU on risk taking and impulsivity in this patient group, large-sample and controlled studies in which repeated tDAU applications will be performed are needed.