The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders has been published by the American Psychiatric Association in 1994. DSM-IV relies upon the same basic concepts as DSM-III and DSM-III-R: explicit diagnostic criteria, multiaxial system, and a descriptive approach that attempts to be neutral with respect to theories of etiology. The DSM-IV revision process has included comprehensive and systematic reviews of the published literature, reanalyses of already-collected data sets and extensive issue-focused field trials. Considerable efforts have been made to ensure that the codes and terms provided in DSM-IV are fully compatible with both ICD-9-CM and ICD-10. According to the authors of DSM-IV, the major innovation of DSM-IV lies not in any of its specific content changes but rather in the systematic and explicit process by which it was constructed and documented.