title: Pain perception in schizophrenia: evidence of a specific pain response profile.
abstract: OBJECTIVE
  Ever since the characterization of schizophrenia, clinicians have noted abnormal pain sensitivity in their patients. The published literature, however, is inconsistent concerning the nature of the change reported. The objective of this study was to characterize the pain response profile of schizophrenic patients by providing both acute and prolonged (i.e., rapidly repeating) painful stimuli to schizophrenic participants and control subjects.
  
  
  METHODS
  Twelve schizophrenic subjects and eleven controls were included in the final analysis. Diagnosis was made according to Diagnostic and Statistical Manual of mental disorders-4th edition, text revision (DSM-IV-TR) criteria.
  
  
  METHODS
  Intermittent, transcutaneous stimulations of the left sural nerve were administered to all participants. Painful sural nerve stimulations provoked a nociceptive flexion reflex response which was measured using an electromyographic recording of the bicep femoris muscle. Pain ratings were obtained using a 0-10 verbal numerical scale. Among schizophrenic participants, the relationship between subjective pain, reflex amplitude, and clinical features was investigated. The Positive and Negative Syndrome Scale, Calgary Depression Scale for Schizophrenia, and Subjective Scale to Investigate Cognition in Schizophrenia were used to evaluate clinical features.
  
  
  RESULTS
  Compared with controls, schizophrenic subjects showed increased sensitivity to acute pain (i.e., lower pain thresholds; P = 0.019), but decreased subjective pain sensitization (P = 0.027). Group differences in subjective pain sensitization were not accompanied by group differences in nociceptive reflex activity (P = 0.260), suggesting supraspinal origins to the change in pain experienced by schizophrenic subjects. Moreover, positive symptoms correlated negatively with pain threshold values among schizophrenic participants (r = -0.696, P = 0.012), suggesting that distortions of thought and function relate to pain sensitivity in schizophrenic patients.
  
  
  CONCLUSIONS
  Results indicate that schizophrenic subjects present a specific experimental pain response profile, characterized by elevated sensitivity to acute pain but reduced sensitivity to prolonged pain.
authors.affiliation: Département de neurochirurgie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Canada.
authors.forename: Mylène
authors.initials: M
authors.lastname: Lévesque
authors.forename: Stéphane
authors.initials: S
authors.lastname: Potvin
authors.forename: Serge
authors.initials: S
authors.lastname: Marchand
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Stip
authors.forename: Sylvain
authors.initials: S
authors.lastname: Grignon
authors.forename: Lalonde
authors.initials: L
authors.lastname: Pierre
authors.forename: Olivier
authors.initials: O
authors.lastname: Lipp
authors.forename: Philippe
authors.initials: P
authors.lastname: Goffaux
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000150:complications / Q000503:physiopathology*; D008297:Male; D010147:Pain Measurement; D058748:Pain Perception; D017288:Pain Threshold; D011618:Psychotic Disorders / Q000150:complications / Q000503:physiopathology; D012018:Reflex; D012563:Schizophrenia, Paranoid / Q000150:complications / Q000503:physiopathology*; D013497:Sural Nerve; D004561:Transcutaneous Electric Nerve Stimulation