Aren't some of the diagnoses included in the DSM there for “political” reasons?
Decisions to include a diagnosis in the Diagnostic and Statistical Manual of Mental Disorders (DSM) are based on a careful consideration of the research underlying the disorder. This is not to say that decisions are made without regard to other considerations. Scientific data cannot be interpreted in a vacuum. Sociological and other considerations must also be taken into account. For example, each proposed new diagnosis carries with it the risk of making a false positive diagnosis (i.e., making a diagnosis when no disorder is present). Since false positives can never be completely eliminated, we must consider instead how to balance the advantages of including the diagnosis in the DSM (e.g., increased detection of a treatable disorder with consequent reduction in morbidity and cost to the patient, his or her family, and to society at large) against the risks of making a false positive diagnosis (e.g., risk of stigmatization, cost and potential morbidity of unnecessary treatment, etc.). However, the overall driving force in the decision to include or exclude a potential diagnosis from the DSM is the availability of scientific data.