Assignment of a psychiatric diagnosis is based upon a complex interpersonal transaction in which a diagnostician's professional training, experience, and skill are applied to the detection of signs and indications of a specific mental disorder in a person who is typically experiencing distress, discomfort, and helplessness. In the ideal case, this determination is construed as an inference from the observations and communications gathered, subject to minimal distortions, if any. In actuality, the attainment of veridical psychiatric diagnosis across all populations and diagnostic categories was an ambitious and elusive goal throughout the twentieth century. By this time, substantial advances in formulating and applying rules of diagnosis have been made, exemplified by the changes in the
Diagnostic and Statistical Manuals
of the American Psychiatric Association from the first to the current fourth edition, the development of observational rating and self‐report symptom scales, and the improvement of interviewing procedures. Nonetheless, problems with the validity of diagnostic judgment persist – a continuing task for the mental health professions throughout the world is to reduce errors and distortions.