Réactivité à la douleur dans les schizophrénies : un phénomène spécifique ou lié au fonctionnement psychique des patients ?

RésuméLa douleur est avant tout une expérience. Cette expérience peut être fortement altérée chez les patients présentant des troubles psychiatriques. La douleur s’exprime, également, et l’expression comportementale peut être modifiée, voire rendue difficilement compréhensible, dans le cas de pathologies psychiatriques sévères. Nous proposons une revue critique de la littérature concernant les anomalies de la réactivité à la douleur observées chez les patients schizophrènes. Ce phénomène est fortement suggéré par la pratique clinique et des études de cas, en particulier dans la littérature historique. Il est cependant mal connu, et il n’existe pas de consensus sur les mécanismes en cause. Il apparaît que la littérature actuelle ne permet pas de conclure à une réelle analgésie chez les patients schizophrènes, mais plus sûrement à un mode d’expression différent de la douleur, en lien avec la pathologie. Dans ce cadre, les travaux récents sur l’approche empathique de la douleur ressentie nous semblent un mode de compréhension pertinent.

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 an analgesic phenomenon but a different behavioral 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 markers 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 show a relative insensitivity to physical pain. We will review and critic the scientific literature in this specific topic. We will see if data are relevant with the neurodevelopmental hypothesis and vulnerability models. Articles are separated in 2 groups, first are clinical or epidemiological studies, and second are experimental studies. 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 decease 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 behavioral response seems to be frequent and may be explored 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 behavioral 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 behavioral expression of pain. Recent research regarding empathy in patients with schizophrenia may be a relevant approach for understanding the un-specificity of pain reactivity impairment in these patients.