Definition of Disorder
Classification is essential for scientific progress in any discipline. This is difficult enough in general psychiatry, but in child psychiatry the diagnostic process is particularly challenging. To begin with, there is less information about natural history, familial patterns, and developmental aspects of most of the childhood behavioral disorders. Because of this, most diagnostic categories have been generated on the basis of what clinicians agree they recognize from clinical descriptions as fitting what they see in their own practice. In addition, the particular group of children seen and the type of clinic to which they go may vary widely among clinicians, thus introducing a referral bias, which will influence clinicians' knowledge of disorders because their perception is influenced by their experience. Adequate epidemiological data to support the phenomenon of clinic-based diagnosis are often not available.