The Textbook of Anxiety Disorders presents chapter authors who are a virtual who's who of practitioners writing about the origins, classification, and treatment of anxiety disorders. The book is an excellent introduction to the literature on anxiety disorders for new students of psychiatry. It covers the biopsychosocial cultural aspects of anxiety disorders and broadly offers the traditional nature versus nurture perspective.

Chapters 1 and 2 cover the history and classification of anxiety disorders. Chapters 3—6 cover the biological aspects, discussing animal models of anxiety, neural circuits of fear and anxiety, anxious traits and temperaments, and neuropsychology. Chapters 7—10 and 39—42 cover the psychosocial-cultural treatments for anxiety and describe the economic impact of anxiety disorders on the health care system. These chapters review cognitive, behavioral, psychodynamic, and evolutionary concepts, which can be used conjointly with medications as the primary treatment for anxiety disorders. The largest part of the book (chapters 11—38) is organized according to categorical DSM-IV-TR diagnostic groups. While this traditional organization makes this overview of all anxiety disorders easy to grasp, many of the treatment sections in each chapter are redundant. Every chapter describes minor variations of the same pharmacological and psychotherapeutic treatment approaches.

A particularly useful component of the book is the "Key Clinical Points" listed at the end of each chapter. These pearls give a nice snapshot of important take-home points. Were the authors to add the evidence supporting these clinical assertions, it would be even more useful to the clinician.

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.

What about the symptoms within the five described anxiety disorders? Are these disorders discrete? Yes and no. Trauma, obsessions, compulsions, and panic help us differentiate these disorders, but phobic symptoms and worry also track across all these disorders as important dimensions. What about the relationship between anxiety and the somatoform disorders? Is obsessive-compulsive disorder best viewed as one of the categorical anxiety disorders, or are hypochondria and body dysmorphic disorders better grouped with obsessive-compulsive disorders as variants?

Other questions are raised. Are anxiety and depressive disorders really dimensional, or are they just discrete disorders that appear in other subpopulations as comorbid disorders? Maybe… we know that in some cases the family genetic history clearly suggests comorbidity of discrete disorders.

What about the fact that some patients, most often recognized in primary care settings, have both subthreshold anxiety and depressive symptoms and have never met the criteria for either a full-blown anxiety or depressive disorder? Is this a manifestation of negative-affective dimensions, or should we consider this a new categorical disorder, called "mixed anxiety-depressive disorder"? The evidence suggests that this mixed disorder is prevalent in primary care settings; these patients have a meaningful functional disability, and they have a higher risk of developing more severe disorders. This is really the reverse of the discussion on dimensions and suggests that in some cases new categorical disorders for DSM-V may be clinically warranted.

Does the treatment of anxiety and depressive disorders offer any clarity to resolving these dilemmas? Yes and no. The fact that benzodiazepines can treat many anxiety disorders yet may make depression worse argues for the categorical approach for some patients. However, the fact that both selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors are generally effective in treating the vast majority of all anxiety and depressive constellations argues that our medications are largely treating dimensions, not categories. Our antidepressants operate much like psychiatric aspirin. We are able to treat the fever of dimensional negative-affective states but do not yet have meaningful specific categorical treatments. Looking at our psychotherapies for treating these disorders, we face a similar finding. Some disorders, like obsessive-compulsive disorder and posttraumatic stress disorder, are best treated with a specific psychotherapy, called exposure response prevention. This argues for a categorical approach. On the other hand, we're able to treat other anxiety disorders and mixed anxiety-depressive states with a growing list of psychotherapies (cognitive-behavioral therapy, interpersonal therapy, dialectical behavior therapy, psychodynamic psychotherapy, and exposure-response prevention). This supports the dimensional conceptions.

What is hopefully clear from this discussion is that the psychiatric field is in flux with "splitters" and "lumpers" in a classic debate. The field of anxiety disorders presented in this book, perhaps reflecting all of psychiatry, is trying to transition to more complicated dimensional models, yet to be clarified, while holding on to clinically useful categories. We are also searching for specific categorical treatments but instead find our current treatments are dimensionally successful but lack some of the specificity we seek.

If we are ever to make a quantum leap forward, we will someday have to move beyond categorical and dimensional descriptions to genomic, pathophysiological, or a more specific etiological understanding of psychiatric suffering.