The effectiveness of a Transdiagnostic Cognitive-Behavioral Treatment will be compared with an improved version of it, in which new intervention techniques were added, pointing out the importance of improving some self-concept dimensions in reducing symptoms of anxiety and depression. In order to prove this, the study design will include two active intervention groups; a standard transdiagnostic intervention protocol will be delivered to one group and an improved version of the same transdiagnostic protocol will be delivered to the other group. The new added techniques targets some self-concepts, namely self-compassion, unconditional self-acceptance and self-esteem. The main goal of the study is to concurrently test effectiveness of these two transdiagnostic approaches in reducing symptoms of anxiety and depression and improving the above-mentioned self-concepts. This non-inferiority trial has the power to detect an effect size larger than Cohen's d = .40 (including 20% attrition at post-test and 6 month follow-up)
