[Schizophrenia and pain reactivity].
INTRODUCTION
Medical practitioners do not for a long time pay enough attention to patient's pain. This approach is in the line of society feelings. Pain was long consider to be a contingency to withstand as showed in Christian's bible or Stoicism's principle. Changes in mentality appear in present times. It Seems obvious that for sociological and scientific reasons pain's care in medical and psychiatric disorders is now an important subject. Recent research in autistic disorders suggest that insensitivity observed in autism is not and analgesic phenomenon but a different behavioural reactivity to pain. Prevalence of schizophrenic disorder is from 0.5 to 1%. It is also a complex disorder that has defied decades of concerted efforts to uncover its origins and attenuate its symptoms. The most promising hypotheses suggest that neurodevelopmental impairment increases the risk of later schizophrenia. Most of recent researches in this topic did focus to trait or state markers. According to the vulnerability models of schizophrenia, trait marker are clinical, psychological, physiological, anatomical or cognitive impairments found in patients with schizophrenia during all the course of the illness and even before the onset. Several lines of evidence (case report, epidemiological studies, experimental studies) suggest that patients with schizophrenia shows a relative insensitivity to physical pain. We will review and critic the scientific literature in this specific topic. We will see if datas are relevant with the neurodevelopmental hypothesis and vulnerability models.


METHODS
An OLDMEDLINE/MEDLINE query was performed to identify 50 articles relevant to our subject. 9 were case report or case series, 21 were clinical or epidemiological studies, 15 were experimental studies and we also found 5 previous review.


RESULTS
Clinical and experimental data strongly suggest a decrease of Behavioural Reactivity to Pain (BRP) but there is a lack of argument to prove a real analgesia. Because schizophrenia is a severe disease with impairment in communication and social skills it may be very difficult to affirm that the insensitivity to pain does really exist for patients. It seems inappropriate at this point to speak about insensitivity or analgesia. We could hypothesis that the decrease of BRP is less a consequence of analgesia than a different way to express emotion in general and pain in particular. It is well known that patients with schizophrenia show communication and thinking impairment, not adapted social skills and also a lack of body representation. However, this decrease of behavioural response seems to be frequent and may be explore by objective research protocol to understand if patients don't feel pain or probably don't express pain by adapted social skills. Furthermore, decrease of BRP may take place in a comprehensive theory of schizophrenia. in the line of stress-vulnerability model. Impairment or lack of behavioural pain reactivity could induce an increasing anxiety level for patient with vulnerability to schizophrenia and a higher risk of onset of the pathology. We may argue that pain stimuli would conduct to a nociceptive stress witch couldn't discharge by usual ways of regulation and behavioural expression of pain. Exploration and interview about pain reactivity in vulnerable to schizophrenia subjects could be interesting to increase a the amount of information in a vulnerability check-up. Further studies in this axis may be useful to test this hypothesis.