Depression is a mental disorder with symptoms such as sadness, emptiness, hopelessness, and decreased interest or enjoyment in most daily activities. The disorder is associated with physical symptoms such as headache, fatigue, anorexia, insomnia, constipation, hypotension, etc (
1). On the other hand, patients suffering from depression have frequently self-reported negative feelings (
2) and lack of control over thoughts and behaviors (
3). The last symptom is associated with the recurrent activation of the cognitive-attentional syndrome (CAS) (
2), which is one of the primary constructs in the metacognitive theory of emotional disorders. The syndrome encompasses a set of psychological processes such as recurrent negative thoughts (concern and rumination), threat-focused attention, and cognitive-behavioral strategies (
4).
According to many studies, CAS is a significant factor in developing mood disorders, including depressive disorder, anxiety disorder, post-traumatic stress disorder, and obsessive-compulsive disorder (
4,
5). Cognitive-attentional syndrome makes individuals suffer from distorted and biased thoughts, which are out of control. This would consequently make their emotional problems permanent and intensified (
6). In other words, this syndrome leads to the adoption of self-regulatory strategies or maladaptive coping behaviors, which are considered useful by the same individual; however, they have opposite effects and make emotional problems last longer (
6). Cognitive-attentional syndrome is rooted in the metacognitive approach to psychological disorders (
7), the removal of which is essential by assisting the patients to detect new approaches to control attention, link to negative thoughts and beliefs, and change metacognitive beliefs creating maladaptive thinking patterns (
5). In this regard, behavioral activation and acceptance and commitment therapy are the two main treatments derived from clinical behavior analysis and metacognitive approaches to depression (
8).
Behavioral activation (BA) is a type of non-pharmacological intervention based on Skinner's psychological model of behavior change, known as functional behavioral assessment (
9). Behavioral activation is underpinned by an assumption indicating that the lack of adequate environmental support or excessive environmental punishment arouse depression. The intervention aims to promote environmental reinforcement and decrease environmental punishment (
10). Jafari et al. (
11) showed that BA is effective in improving depressive symptoms and quality of life by helping the individual to distance himself from the psychological processes of accreditation to painful emotions. Timurpour et al. (
12) showed that behavioral activation therapy is significantly effective in increasing cognitive flexibility and emotional resilience in patients with depressive disorder. Acceptance and commitment therapy (ACT) is also one of the third-wave psychological therapies considered not only in the field of positive psychology but also in the treatment of psychological damages and disorders such as depression and anxiety. It is based on mindfulness (
13), i.e., the conscious involvement of awareness along with openness, interest, and acceptance in one’s here-and-now experiences(
14). In this regard, when individuals view their personal experiences (i.e., thoughts and feelings) with openness and acceptance, even the most painful of which seems to be less threatening and more tolerable (
15).
Previous studies have revealed the effectiveness of BA in decreasing depression. For example, Kellett et al. (
16) reported that behavioral activation can be an effective depression treatment option that shows some clinical promise. Szuhany et al. (
17) reported that BA may be a useful strategy for improving depression and increasing exercise. Babakhanzadeh et al. (
18) showed that cognitive therapy, with emphasis on executive functions, reduced cognitive-attention syndrome, and improved the sense of coherence among students. Melli et al. (
19) reported that metacognition may have an important role in health anxiety in clinical samples. The effectiveness of ACT in decreasing depressive symptoms was also confirmed (
20,
21). A-Tjak et al. (
20) showed that ACT, as well as reductions in avoidant and anxious attachment, predicts symptom reduction after psychological treatment for depression. Kazemeyni et al. (
21) showed that ACT significantly reduced the rate of depression and increased psychological flexibility in women with depression.
However, it is not known which intervention can have the highest positive effects on CAS in individuals suffering from depression. Given that depression is one of the most common psychological problems that is associated with huge costs at the individual and social level, it is necessary to take effective interventions and basic steps to prevent and treat psychological problems. Identifying the best and most cost-effective treatment is also essential to reduce disease rates and treatment.