The Diagnostic and Statistical Manual of Mental Disorders is the text that is used by mental health professionals to  assess, categorize and name mental disorders in people of all ages.   The assesment is complete with five axis:  Axis I describes the Clinical Disorders, Axis II describes prominent maladaptive personality features and mental retardation, Axis III describes the general medical condition (with ICD-9-CM or medical codes), Axis IV describes psychosocial and and environmental problems and Axis V provides a numerical range for the individual's Global Assessment of Functioning.  In the book the diagnoses are explained and there is a helpful "decision tree" to assist in narrowing down the possible diagnoses.There is a student handbook or desk reference that is helpful for the new practitioner or parent.