The aim of this study is to assess the efficacy of a Transdiagnostic Internet-based Protocol (Emotion Regulation Protocol) for the treatment of Emotional Disorders (ED) (major depression disorder, dysthymic disorder, obsessive-compulsive disorder and four anxiety disorders: panic disorder, agoraphobia, generalized anxiety disorder, and social anxiety disorder) both in terms of efficacy regarding depressive and anxiety symptomatology and its potential impact on higher-order psychological dimensions (neuroticism/behavioral inhibition and low positive affect/behavioral activation) in a community sample. It will also be tested the differential effect of a specific treatment component based on positive psychology techniques in positive affect. The main hypotheses are: 1) both modalities of the protocol (TP and TP+PA) will be more effective than the WL condition in the primary outcome measures. Investigators also expect scores on positive affect to be higher in the TP+PA condition than in the TP condition.

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 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 Diagnositc and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (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 the other hand, Evidence-based psychological treatments (EBPT) have shown efficacy in the treatment of ED, however, less than 50 % of people with ED receive treatment and causes include costs, time of application and the lack of well-trained professionals. 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 systematic 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 very few transdiagostic internet-based treatments have been developed and tested by means of randomized controlled trials so far.

The main objective of the treatment components of the Unified Protocol (UP) is to train patients in the regulation of negative emotions or negative affect (NA), but less attention has been paid to the inclusion of treatment components directly targeting positive affect (PA) regulation.

Investigators of this research group (LabPsiTec) have developed a traditional transdiagnostic treatment that is partly based on the UP and it has been added a specific component of positive affect regulation in order to more directly target the regulation of positive affect. The study will include three conditions: 1) Transdiagnostic protocol (TP); 2) Transdiagnostic protocol + positive affect component (TP+PA); and 3) Waiting list control group (WL).

The main hypothesis is that both modalities of the protocol (TP and TP+PA) will result more effective than the WL condition in the primary outcome measures. Investigators expect scores on positive affect to be higher in the TP+PA condition than in the TP condition.

Inclusion Criteria:

• Be 18 years old or older.
• Meeting the DSM-IV diagnosis criteria of emotional disorder (panic disorder, agoraphobia, social anxiety disorder, generalized anxiety disorder, obsessive-compulsive disorder, major depression disorder and dysthymia).
• Providing written, informed consent.
• Being able to understand and read Spanish.
• Having daily access to the Internet in their natural environment.

Exclusion Criteria:

• Being diagnosed a severe mental disorder (people with the following mental disorders will be excluded from the study: schizophrenia, bipolar disorder and personality disorders from clusters A and B).
• Being diagnosed an alcohol and/or substance dependence disorder.
• The presence of high suicidal risk.
• A medical disease or condition which prevent the participant from carry out the psychological treatment.
• Receiving another psychological treatment while the study is still ongoing.
• The increase and/or changes in the medication of participants receiving pharmacological treatment during the study.