The symptom index is a quick and convenient overview that can help form the basis for your differential diagnosis. It has a very different point of departure from the DSM-IV-TR Differential Diagnosis Tables. The tables are organized syndromally just as is DSM-IV-TR. Each disorder is defined by a cluster of symptoms that frequently co-occurs and that shares aspects of course, family history, and treatment response. As with the decision trees in Chapter 2, the symptom index helps you go in the reverse direction—from symptom to syndrome. Some of the symptoms covered in this chapter have also served as the starting point for decision trees presented in this book. However, many more symptoms are included here to provide a more fine-grained depiction of the system than was possible with the decision trees.