The aim of this study is to assess the differential effect of two transdiagnostic treatment protocols for emotional disorders (ED) (depression and anxiety disorders) using a randomized pilot study design: a) a transdiagnostic treatment protocol (TTP) based on the Unified Protocol; and b) a version of this protocol that also includes a specific component to address the regulation of positive affect (TTP+PA). Another aim was to assess the acceptability of both treatments by patients. It was hypothesized that the intervention would result in significant differences in favor of the TTP+PA protocol in all measures. Regarding acceptability, it was hypothesized that both treatments (TP and TP+PA) would be well-accepted by the two groups of participants.

ED are highly prevalent mental disorders and one of the main causes of disability worldwide. Currently, there is evidence showing the efficacy of transdiagnostic treatments for anxiety disorders, and for comorbid depression and anxiety disorders. An important line of research within the transdiagnostic treatment of ED was initiated by D. H. Barlow. Barlow's theory of triple vulnerability emphasizes the underlying vulnerabilities that are common to ED and help to explain the comorbidity among these diverse conditions. A central aspect within this theoretical perspective is the role of emotion regulation in ED. The regulation of negative emotions in ED has received a great deal of attention in cognitive behavior therapy (CBT) research, and more recently in transdiagnostic ED models like the UP developed by Barlow's team. However, although Barlow underscored the role of low PA in the onset and maintenance of ED, the main objective of the treatment components in the UP is to train patients in negative affect (NA) regulation, but less attention has been paid to the inclusion of treatment components to directly target PA regulation. Moreover, literature has shown that higher levels of PA are associated with better physical and psychological health, healthier lifestyles, and better general functioning. Consequently, an important treatment goal from a transdiagnostic treatment approach would be to increase PA while decreasing NA.

The aim of this study is to compare the differential effect of two transdiagnostic treatment protocols for ED using a randomized pilot study design: a) a transdiagnostic treatment protocol (TTP) based on the Unified Protocol; and b) a version of this protocol that also includes a specific component to address the regulation of positive affect (TTP+PA). Another aim is to assess the acceptability of both treatments by patients. It was hypothesized that the intervention would result in significant differences in favor of the TTP+PA protocol in all measures. Regarding acceptability, it was hypothesized that both treatments (TP and TP+PA) would be well-accepted by the two groups of participants.

Inclusion Criteria:

• 18 years old or older
• meeting the DSM-IV diagnostic criteria for ED (major depression disorder, dysthimic disorder, generalized anxiety disorder, social anxiety disorder, panic disorder, agoraphobia, obsessive-compulsive disorder, anxiety disorder not otherwise specified, unipolar mood disorder not otherwise specified)
• ability to understand and read Spanish

Exclusion Criteria:+

• bipolar disorder
• schizophrenia
• risk of suicide
• receiving another psychological treatment during the study
• in the case of receiving pharmacological treatment, an increase and/or change in this treatment during the study period (a decrease in pharmacological treatment is accepted)