Emotional disorders (ED) (anxiety and mood disorders) are among the most prevalent mental disorders, with a life prevalence of 29% and comorbidity rates that range between 40 and 80%. If they are not adequately treated the course is often chronic, and them significantly affect important functioning areas such as work and social relationships. Thus, these data strongly suggest efficacious and efficient treatments are needed in order to address this important health problem. The classification and differentiation of mental disorders carried out in manuals like the DSM and the ICD has played an important role in the emphasis placed on the research about the treatment of specific disorders; however, it has also been a problem in the dissemination of evidenced-based treatments due to the difficulties in training the clinicians in the variety of the available disorder-specific programs. In fact, less than 50% of people suffering from emotional disorders receive a psychological treatment; and this is also accounted for by its costs and time of application. As a consequence, many people decide not to search for psychological treatment. In addition, epidemiological studies have shown that at least 55% of people suffering from an anxiety disorder suffer from another anxiety disorder at the moment of the assessment, and this prevalence rate is up to 76% when different lifespan diagnoses are taken into account. This high comorbidity rate indicates that the different ED share important characteristics and it has been proposed that this overlapping is accounted for by common biological and psychological vulnerabilities that along with psychosocial stress factors leads to different manifestations of the same vulnerability, i. e., the different mood and anxiety disorders. Thus, a Transdiagnostic approach could help overcome these barriers.

Transdiagnostic approaches have implications in the treatment of psychological disorders as a number of treatment protocols have been developed based on this perspective. Clark has distinguished three perspectives in transdiagnostic cognitive-behavioral therapy: a) The transdiagnostic practice, a pragmatic perspective that includes components of various disorder-specific intervention protocols whose aim is to determine which are the active components in samples with those disorders. The contributions of Norton, Andrews and Titov, and the study: Coordinated Anxiety Learning and Management (CALM) belong to this category. b) The transdiagnostic theory, that specifies a theoretical framework which outlines the common psychological constructs that influence the maintenance of ED. For instance, the tripartite model of anxiety and depression, with positive and negative affect as relevant constructs. c) The Unified Protocol. The Barlow's team has designed a protocol, adequate for the treatment of ED which focuses on four essential aspects: to increase present-focused emotional awareness, to identify and modify emotional avoidance patterns, to promote the cognitive flexibility and to facilitate exposure to avoided situations and sensations.

Another aspect that could enhance the dissemination of evidence-based treatments as well as considerably reduce the costs is the use of the Internet. A number of sistematic reviews has shown that Internet-based treatments yield similar results when compared to face-to-face therapy. Nevertheless, most of these programs are focused on a single disorder since a few Transdiagostic Internet-based treatments have been developed and tested by means of randomized controlled trials so far. Furthermore, no studies on efficacy of Internet-based Transdiagnostic vs Treatment as usual (TAU) have been carried out in specialized care. Therefore, we have developed a Transdiagnostic Internet-based protocol treatment (Emotion Regulation Protocol) based on the Unified Protocol proposed by Barlow, that also includes components of emotion regulation and acceptance.

The aim of this study will be to test the efficacy of a Transdiagnostic Internet-based protocol (Emotion Regulation Protocol) for the treatment of emotional disorders by means of a randomized controlled trial in a sample made up of participants from specialized care of the Spanish public mental health system. The study will include two conditions: a) Transdiagnostic Internet-based treatment protocol and b) TAU. The main hypothesis is that the Transdiagnostic protocol will be more efficacious than TAU and that will obtain a good acceptance by patients and mental health professionals. We also expect the online Transdiagnostic protocol to be more efficient when compared with TAU (e. g., a significant greater number of patients which receive a psychological treatment, a significant reduction of the waiting lists and costs such as hours of clinical assistance and hours of face-to-face treatment, etc.).