The most prevalent mental disorders, anxiety and mood disorders, are associated with both functional and morphological brain changes that commonly involve the 'fear network' including the (medial) prefrontal cortex, hippocampus and amygdala. Patients suffering from anxiety disorders and major depressive disorder often show excessive amygdala and reduced prefrontal cortex functioning. It is, however, still unclear whether these brain abnormalities disappear or diminish following effective treatment.