The most valuable contributions for more advanced psychiatrists, reflecting the state of our field, are a range of interesting discussions dispersed throughout the book focusing on the most important controversies and issues in the anxiety disorders arena. The major issues discussed are the themes of categorical vs. dimensional models of anxiety disorders, the spectrum of symptoms, mixed disorders; subthreshold disorders, threshold categorical disorders, and comorbidity with other psychiatric disorders. The book also raises the specificity of our pharmacotherapy and psychotherapy. While highlighting these issues for all the anxiety disorders, it seems clear they are pervasive controversies for all of psychiatry across all psychiatric disorders. These issues, discussed in many chapters, are brought into clear focus in chapter 15, titled "Mixed Anxiety-Depressive Disorder: An Undiagnosed and Undertreated Severity Spectrum Disorder?" by Fawcett, Cameron, and Schatzberg. Anxiety and depression frequently run together. Are they two separate disorders? Yes and no. Using the categorical approach, we view these two disorders as discrete syndromes, often recognized in different groups of patients. Seen as distinct disorders, they have different prognoses and may require different treatment approaches. Yet, as clinicians, we also see a significant group of patients simultaneously suffering with both anxiety and depressive symptoms. Are these two dimensions of a larger group of negative-affect disorders with the same underlying genetic diathesis? This appears to be true for a subset of patients who are better viewed as having dimensions of a negative-affect disorder crossing categorical boundaries. This conceptualization allows us to recognize different outcomes than we might see in the discrete disorders alone.