La douleur chronique en psychiatrie : comorbidité et hypothèses

Over previous decade, psychiatry has become peripheral to pain management and anaesthesiology has moved onto centre stage with ever more sophisticated interventions, including radiofrequency neurolysis, implanted medication pumps, and spinal cord stimulators. However, a sizeable sample of patients with chronic pain is not achieving satisfying remission. With regard to the high prevalence of psychiatric disorders among those patients, psychiatry has an important amount to offer this field, at least as much as any other single discipline. Since Freud’s psychodynamic theory of hysteria, as an explanation for chronic pain without a located physical basis, other important contributions from psychiatry have been made, including the concept of pain-prone disorder as a variant of depression and the liaison psychiatrist George Engel’s biopsychosocial medical model.Nineteen consecutive patients with chronic pain, 12 females and 7 males, were admitted to a 5- or 10-days inpatient program in a psychiatric department. None of those patients were working at the time of their admission. The main purpose of this program was to examine psychiatric comorbidity and the need for further psychiatric follow-up. This sample is described in terms of the two first axes of the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) nosology. Diagnoses were retrospective for 10 patients (52.6%) and prospective for the others (47.4%). The retrospective diagnoses were those mentioned in the patient file. Results regarding personality disorders are with the exclusion criteria not applied for other personality disorders.Not surprisingly, with chronic pain disorder excepted, depressive disorders were the most frequent diagnoses on axis I (diagnosed in 52.6%). Major depressive disorder was diagnosed in 36.8% (current episode = 26.3%), while dysthymic disorder was diagnosed in 15.8%. Anxious disorders as social phobia, post-traumatic stress disorder and generalised anxiety were each respectively diagnosed in 15.8%. Substance misuse or dependence was diagnosed in 21.1%. Schizophrenia and dementia were each respectively diagnosed in 5.2%. Among somatoform disorders, chronic pain disorder was diagnosed in 78.9%. 10.5% had no diagnosis on axis I. Personality disorder was diagnosed in 73.7%. Histrionic personality disorder and avoidant personality disorder were each respectively diagnosed in 26.3%. Other diagnoses on axis II are detailed.Previous studies have shown such a positive association between pain and depression. Those results are summarised. Evidence supporting a direct link between these two variables is less robust. Although chronic pain as a variant of depression is a useful psychodynamic concept in some individual cases, it seems insufficient as a general model of chronic pain. Other hypothesis are reviewed, especially those which conceptualise both depression and chronic pain as relevant to a unique underlying process. This process may be conceptualised as a proneness to generalise negative events as acute pain or fear. Previously, Swanson advanced that chronic pain may belong to the category of emotions. According to such a model, analogies can be used to compare acute and chronic pain with fear and anxiety and also with sadness and depression. This proneness to generalise negative emotional events may be adequately described by a unique personality trait like Eysenck’s Neuroticism or Cloninger’s Harm Avoidance. Previous results supporting this hypothesis are reviewed. The last six patients were given the Temperament and Character Inventory—Revised (TCI-R). Preliminary findings are discussed. Despite several limitations, those results are consistent with our hypothesis, showing homogenous Harm Avoidance scores.