Objectives: To review the scientific literature regarding pain and schizophrenia, examine the empirical basis for the reported pain insensitivity of schizophrenia, and to emphasize the distinction between behavioral responses to pain or self-reported pain and physiologic response to painful stimuli.
Methods: A Medline/Oldmedline search was conducted through 2006 using the key words schizophrenia and psychosis combined with pain and related terms designated by the International Association for the Study of Pain. Out of 431 articles initially identified, 57 were considered relevant and classified in 4 groups: case reports (n=9), clinical studies (n=23), experimental research (n=20), and review articles (n=5).
Results: Case reports and clinical studies reported reduced pain reactivity in patients with schizophrenia compared with healthy controls or other psychiatric patients. Similarly, experimental studies using self-report measures of pain reactivity generally reported higher pain perception thresholds in patients with schizophrenia. However, the only experimental study using a neurophysiologic measure of pain reactivity (the nociceptive RIII reflex) demonstrated a normal pain threshold in schizophrenia.
Discussion: Review of clinical and experimental data indicates that in most situations behavioral pain reactivity and self-reported responses to pain are reduced in schizophrenia. However, there is little or no physiologic evidence supporting pain insensitivity in schizophrenia. It can be suggested that the widely accepted notion of reduced pain sensitivity in schizophrenia is related more to a different mode of pain expression than to a real endogenous analgesia. Further studies are required and potential directions for future research are proposed to clarify this issue.