Study of the effects of cognitive behavioral therapy versus dialectical behavior therapy on executive function and reduction of symptoms in generalized anxiety disorder

Abstract Introduction The effects of dialectical behavior therapy on generalized anxiety disorder have not been examined to date, whereas cognitive behavioral therapy is a well-known psychotherapy for generalized anxiety disorder. Objectives This study investigated the effects of cognitive behavioral therapy versus dialectical behavior therapy on executive function and reduction of symptoms in generalized anxiety disorder. Method In the present study, 72 generalized anxiety disorder patients were randomly assigned to one of two groups: dialectical behavior therapy or cognitive behavioral therapy. Evaluations were performed at baseline, post-test, and three months after interventions as a follow-up. Measures included the Structured Clinical Interview for DSM-IV Axis I disorders, the Generalized Anxiety Disorder scale, the Beck Anxiety Inventory, the Beck Depression Inventory, the Tower of London Task, and the Wisconsin Card Sorting Task.Results: The results of the present study showed that both groups had reduced scores for depression and anxiety and increased scores for executive function after the psychotherapies. These changes were maintained at follow-up. Conclusion Although depression and anxiety symptoms were significantly reduced by cognitive behavioral therapy, dialectical behavior therapy was more effective for improving executive function.


Introduction
Generalized anxiety disorder (GAD) is characterized by significant worry about several events over the past six months. The disorder is difficult to control and is associated with physical symptoms such as restlessness, sleep problems, and muscle tension. 1 There is a two-to-one ratio of women to men in this disorder. Its comorbid disorders are social phobias, specific phobias, depression, and panic disorder. 2 Problems with executive function (EF) affecting planning, problem solving, and psychological flexibility have already been confirmed in patients with GAD by numerous studies, 3,4 but it is not yet entirely clear whether psychotherapy can improve these problems in GAD patients. Executive function is a term that encompasses a set of neuropsychological strategies such as thoughts, psychological flexibility, problemsolving, planning, and emotion regulation, and is also associated with job performance. 5 Problems with EF may lead to real-life problems that manifest as behavioral problems. Some deficiencies related to EF are related to the symptoms of GAD and helping to correct them will help to reduce the severity of the symptoms of this disorder. 6 In recent years, many researchers have tried to offer treatments for anxiety disorders, especially GAD. Many studies have shown that although the basic treatment for GAD is medication, about two-thirds of patients continue to show symptoms even after a course of medication. Furthermore, medication has been unable to reduce the severity of anxiety. 7 Cognitive-behavioral therapy (CBT) aims to reduce the severity of mental disorders by changing behaviors and cognitions. 8,9 CBT for anxiety disorders mainly focuses on changing thoughts and beliefs using behavioral and cognitive techniques. 10  However, one of the differences between DBT and emotion regulation therapy is that, in addition to emotion regulation, DBT also addresses distress tolerance, mindfulness, and interpersonal relationships, which can help patients significantly. 22 The results of a study of the effectiveness of emotion regulation therapy for GAD showed that this treatment resulted in significant improvements in anxiety, attention inflexibility, quality of life, and emotional problems. 23,24 Therefore, the present study aimed to compare the effects of DBT and CBT on EF in GAD for the first time.

Participants
The study was registered on Iranian Registry prior psychotherapy for at least 6 months before this study, and level of education higher than the eighth grade. Also, exclusion criteria were other major mental disorders (major depression, psychosis, or alcohol or drug use disorder), serious neurological disorders or severe physical illness, and being absent from more than two sessions. The therapy process is illustrated in Figure 1.

Cognitive behavioral therapy
This protocol was adapted from Covin et al. 25 The

Dialectical behavioral therapy
This protocol was adapted from the standard DBT manual. 26  There were also sessions covering information on interpersonal effectiveness techniques, tolerating painful emotions, and techniques to help patients develop healthy relationships.

Therapists
The therapists were two professional psychologists; both had been trained in CBT and DBT. The therapists were also supervised by two professional psychologists during the therapy.

Demographic information
Demographics

Tower of London Task (TOL)
The TOL is a planning task originally designed by Tim Shallice. This task employs three balls of differing colors and scores range from 0 to 36. 37,38 The TOL is a well-known tool for evaluation of frontal lobe functions and planning abilities in clinical individuals. 39

Wisconsin Card Sorting Task (WCST)
This task includes four types of cards that differ by quantity, color, and shape. The WCST assesses cognitive flexibility and problem-solving. 40

Statistical analyses
The Statistical Package for the Social Sciences

Descriptive statistics
The participants were 26 men and 46 women and all participants were ethnic Persians. Participants were randomly allocated to a DBT or a CBT group, including 24 women (66.6%) and 22 women (64.7%) respectively.
Additionally, 33 members of the CBT group and 34 members of the DBT group completed the study. Major comorbid disorders included: substance use disorder (8.1%), major depressive disorder (16.2%), and panic disorder (17.5%). Thirty-one of the 72 patients with GAD had previously engaged in psychotherapy. All demographic information is provided in Table 1.

Anxiety symptoms
Anxiety ranges reduced over time in both the DBT and the CBT groups three months post-intervention and nearly maintained the reduction at three months' followup. In general, BAI and GAD-7 scores diminished over time in both groups, demonstrating decreased anxiety severity after interventions. Although participants had symptom levels above the cut-offs at baseline, after the interventions they had symptom severity below the cut-offs. Furthermore, the CBT group exhibited greater change than the DBT group (Tables 2 and 3).

Depression symptoms
Depression ranges reduced over time in both the DBT and the CBT groups three months post-intervention and nearly maintained the reduction at three months' follow-up. Furthermore, the CBT group exhibited greater change than the DBT group (Tables 2 and 3).

Problem-solving and cognitive flexibility
All subscales of the WCST, including average error, non-perseverative error, perseverative error, and correct responses changed over time in both the DBT and the CBT groups, demonstrating improved cognitive flexibility and problem-solving, and these changes remained nearly the same after three months of followup. Changes were greater in the DBT group than in the CBT group for all WCST subscales.

Planning and goal-directed behaviors
There was improvement across EF measures in both the DBT and the CBT groups. Higher scores indicated better planning after three months of intervention and the improvement was nearly maintained at three months of follow-up. All subscales had varied more in the DBT group than in the CBT group after the interventions.

Discussion
Psychological psychotherapies such as DBT and CBT are effective and efficient for solving psychological problems. This is the first study to compare the effects of DBT and CBT on EF and symptom severity in GAD.
In this study, we aimed to evaluate the effectiveness of DBT and CBT for alleviating anxiety and depression symptoms and improving goal-directed behaviors, planning, problem-solving, and psychological flexibility. This study, like any other study, has its limitations.
One of these limitations is the small sample size.
It is suggested that a larger sample size be used in future studies to enable generalization of the findings.
Furthermore, this study was conducted in Iran and the subject should be studied in other communities. Finally, it would be good to use DBT for other anxiety disorders such as specific phobias and social phobia and compare its effects with those of CBT and third-wave behavioral therapies.

Conclusion
In this study, the effects on GAD of DBT and CBT were compared. The results showed that although CBT reduced symptoms of anxiety and depression, DBT led to improved EF in patients with GAD. These findings will be useful to support future research into use of psychotherapy for GAD. Also, the application of DBT to other mental disorders that involve problems with emotion regulation and EF should be able to improve therapy for mental disorders and reduce the severity of mental disorders.

Disclosure
No conflicts of interest declared concerning the publication of this article.