The transdiagnostic approach argues that the common features are needed to be taken into account [e.g. distress intolerance (DI), intolerance of uncertainty (IU), worry)] underlying emotional disorders rather than evaluating them separately due to the fact that the dissection of anxiety disorders has increased with each emerging version of the Diagnostic and Statistical Manual of Mental Disorders (DSM), in which the classification of anxiety disorders resulted in an increased number of intervention protocols for each disorder. This also caused an increase of comorbidity among anxiety disorders. Transdiagnostic approach offers a unified protocol (UP) for strengthening the common features, and thereby both preventing the emergence of emotional disorders or intervening the symptom severity of emotional disorders, which can be applied to different types of emotional disorders. The main aim of this study is to develop a UP which is planned to be applied as a group therapy. The UP will include interventions developing the levels of common transdiagnostic features (DI, IU and worry). The study's second aim is to investigate the effect of the developed UP on DI, IU and worry. The third one is to search the effect of the developed UP on symptom severity levels of anxiety disorders. Fourthly, this study will search if the levels of transdiagnostic common features (DI, IU and worry) will predict the levels of symptom severity of anxiety disorders'.

The transdiagnostic approach argues that common features are needed to be taken into account [e.g. distress intolerance (DI), intolerance of uncertainty (IU), worry] underlying emotional disorders rather than evaluating them separately since the dissection of anxiety disorders has increased with each emerging version of the Diagnostic and Statistical Manual of Mental Disorders (DSM), in which the classification of anxiety disorders resulted in an increased number of intervention protocols for each disorder. That is why an increase in comorbidity among anxiety disorders is observed. The transdiagnostic approach offers a unified protocol (UP) for strengthening the common features, thereby preventing the emergence and intervening in several emotional disorders.

As part of dissertation, the main aim of this study is to develop UP in Turkish, and measure the effectiveness of the UP on anxiety disorders and the transdiagnostic features. The UP is planned in group therapy format and includes interventions strengthening the common transdiagnostic features (DI, IU, and worry). This protocol is based on cognitive behavioral therapy (CBT) model. The sessions in the protocol are planned as follows:

Session 1 is assessment session and Session 2 is on psychoeducation, which mainly intend to introduce the CBT model. In session 3, emotions are discussed, revealing that emotions point out what is important for us in life. In session 4, 5 and 6, thoughts are worked on. The participants learn to deal with worry and to challenge unfunctional thoughts and generate alternative explanations. Session 7 focuses on behaviors, in which the role of behaviors and the things that can/cannot be controlled are discussed. Session 8 includes a review of what has been learnt during the group therapy and an evaluation on maintaining the accomplishments. In addition, a follow-up session is planned after one month.

In this study, there will be an intervention (UP) group and a control group. The participants will be assigned to the groups randomly. The measurements are the Distress Intolerance Scale (DTS), Intolerance of Uncertainty Scale-12 (IUS-12), Penn State Worry Questionnaire (PSWQ), Metacognitions Questionnaire-30 (MCQ-30), Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder Assessment (GAD-7).

The uniqueness of this protocol is to be the first UP in Turkish with its own order. It is expected to promote transdiagnostic studies in Turkey. This research is also important in contributing to the literature on transdiagnostic studies, which offer an alternative to comorbidity and a decrease in the symptom severity of anxiety disorders.

Inclusion Criteria:

• Being diagnosed with at least one of the following disorders in the pre-interview (SCID 5 interview for diagnosis): generalized anxiety disorder (GAD), panic disorder (PD), social anxiety disorder (SAD) or anxiety disorder not otherwise specified (NOS).

Exclusion Criteria:

• Active substance use or having a psychiatric history related to substance use
• Having a co-diagnosis of psychotic disorders or bipolar disorders
• Receiving active psychotherapy support
• Being not graduated from primary school

There is no plan to share because of the ethical concerns of the participants' privacy.

In this study, single-blind procedure will be applied to reduce biases. For this purpose, participants will be informed only about the general procedure of group therapy (e.g. general focus of the group therapy, number of sessions, duration of sessions, number of participants) but will not be informed about which intervention they receive and which group they are assigned.