The term psychopathology may also be used to denote behaviours or experiences which are indicative of mental illness, even if they do not constitute a formal diagnosis. For example, the presence of an hallucination may be considered as a psychopathological sign, even if there are not enough symptoms present to fulfill the criteria for one of the disorders listed in the DSM.

In a more general sense, any behaviour or experience which causes impairment, distress or disability, particularly if it is thought to arise from a functional breakdown in either the cognitive or neurocognitive systems in the brain, may be classified as psychopathology.