Pain perception in people diagnosed with schizophrenia: where we are and where we are going

The relationship between schizophrenia and diminished perception of pain has generally been confirmed in empirical studies, but the underlying mechanism is rarely addressed by researchers. This paper, based on the systematic review method, relates the study results to the theory of pain processing in order to improve our understanding of this phenomenon. An attempt is made to provide answers to two fundamental questions, namely: (1) Are the diminished pain thresholds independent of the type of stimulation applied? (2) What is the mechanism behind the disturbances in pain processing in people diagnosed with schizophrenia? The main conclusions are that: (1) schizophrenia is associated with pain insensitivity only when subjective pain assessment is applied; (2) the physiological and basic affective responses to pain are intact, but the complex psychological elaboration seems to be impaired; and additionally (3) theses regarding global pain threshold elevation should be formulated with caution, because the majority of studies employ only electrical or thermal stimulation. Moreover, a hypothesis concerning the lack of pain appreciation resulting from disturbances within the Body–Self is developed to explain the impairment of pain processing in the sensory-discriminative, affective, and cognitive dimensions. Suggestions for future research directions are provided.