A mental disorder (such as depression, anxiety, or bipolar disorder) may be classed as related to another medical ailment in modern psychiatric classification systems. This diagnosis is given when evidence from the history, physical examination, or laboratory data indicates that the disturbance is the direct pathophysiological consequence of another medical disease, according to DSM-5. This method has an inherent flaw: by definition, a descriptive classification system should not take into account the disorder's aetiopathogenesis. The diagnosis is, in fact, the result of aetiopathogenic criteria (the disorder is due to a general medical condition).
