The aim of this study is to analyze the feasibility of a blended transdiagnostic group protocol for the treatment of depression and anxiety disorders (emotional disorders) in a one-group clinical trial.

Emotional disorders are the most prevalent mental disorders and they affect the lives of millions of people across the globe. There is an important body of research showing the efficacy of cognitive-behavioral treatments (CBT) for anxiety and depressive disorders (emotional disorders). However, the dissemination and implementation of evidence-based CBT is still one of the principal challenges for research and clinical practice. Over the past two decades, different approaches on how to improve the dissemination and implementation of evidence-based treatments have emerged. In this sense, one important line of research is the transdiagnostic approach to the treatment of emotional disorders. Transdiagnostic treatments "apply the same underlying treatment principles across mental disorders, without tailoring the protocol to specific diagnoses". Broadly, transdiagnostic treatments are based on the premise that the commonalities of psychological disorders outweigh their differences, and that the observed differences (symptoms) are specific manifestations of broader, underlying common psychopathological processes. A number of meta-analyses have shown the efficacy of transdiagnostic treatments. This approach has implications for treatment and clinical practice. For instance, comorbid presentations can be targeted more appropriately, and the costs of training are lower because only one protocol is needed for a range of disorders. Traditionally, transdiagnostic treatments have focused on the regulation of negative affect or neuroticism and less attention has been paid to the regulation of positive affect. However, more recent approaches have emerged that acknowledge the importance of targeting positive affect in addition to negative affect to improve treatment outcomes. Our research group has developed a transdiagnostic protocol that incorporates a component for the regulation of positive affect, with results that support its efficacy in a sample of community patients.

Another approach that could enhance the dissemination and implementation of evidence-based CBT as well as considerably reduce the costs is the use of the Internet to deliver treatments. A number of systematic reviews have shown that Internet-delivered treatments are effective and that they work as effectively as face-to-face psychotherapy. In the context of Internet-delivered treatments, one possibility is the combination of face-to-face and Internet-delivered therapy, also known as blended treatments. The main advantage of blended treatments is its lower cost in comparison with traditional face-to-face psychotherapy. Moreover, blended treatments might be a good alternative for those patients less likely to benefit from guided or unguided Internet-delivered treatments (with no face-to-face contact). On the other hand, group psychotherapy can also help to reduce the costs of therapy. The literature has shown that there are no differences between individual and group CBT for anxiety and depressive disorders.

In spite of the advantages of group CBT, in the specific field of transdiagnostic treatments, research has mainly focused on individual transdiagnostic treatments. Moreover, to our knowledge, no studies have been published that combine blended and group delivery formats to provide transdiagnostic treatments for emotional disorders. The combination of these two treatment approaches to deliver a transdiagnostic treatment might be a highly cost-effective treatment strategy for these disorders. This ultimately could contribute to the dissemination and implementation of evidence-based transdiagnostic CBT.

The goal of this study is to conduct a feasibility trial of a blended transdiagnostic group protocol for the treatment of emotional disorders. The treatment is a transdiagnostic CBT protocol with strategies for the regulation of both negative and positive affectivity.

Inclusion Criteria:

• Aged 18 years old or older
• DSM-5 diagnosis of emotional disorder (panic disorder, agoraphobia, generalized anxiety disorder, social anxiety disorder, major depressive disorder, dysthymic disorder, other specified/unspecified depressive disorder, other specified/unspecified anxiety disorder, obsessive-compulsive disorder)
• Fluent in Spanish
• Daily access to the Internet at home; email address

Exclusion Criteria:

• Diagnosis of a severe mental disorder (schizophrenia, bipolar disorder, substance/alcohol use disorder)
• High risk of suicide
• Receiving another psychological treatment during the study period
• Changes and/or increases in pharmacological treatment during the study period (a decrease is accepted)

Individual participant data will be available after deidentification.

The data will be available immediately following publication.

The data will be available to anyone who wishes to access them.