CBT was primarily developed through a merging of behavior therapy with cognitive therapy. While rooted in rather different theories, these two traditions found common ground in focusing on the "here and now", and on alleviating symptoms. Many CBT treatment programs for specific disorders have been evaluated for efficacy and effectiveness; the health-care trend of evidence-based treatment, where specific treatments for symptom-based diagnoses are recommended, has favored CBT over other approaches such as psychodynamic treatments. In the United Kingdom, the National Institute for Health and Clinical Excellence recommends CBT as the treatment of choice for a number of mental health difficulties, including post-traumatic stress disorder, OCD, bulimia nervosa and clinical depression, and for the neurological condition chronic fatigue syndrome/myalgic encephalomyelitis.