Objective: Whether schizophrenic patients are hypoalgesic or feel pain in the same manner as unaffected individuals can affect the primary care of schizophrenic patients, which often involves an assessment of pain severity made by a medical provider. This study was developed to explore the pain sensitivity of schizophrenics under conditions similar to those of a medical examination that included investigating for sites of pain.
Methods: We developed 2 experimental models of pain induction using either pressure or ischemia and used them with 35 schizophrenic patients and 35 controls to record: (1) the stimulus intensity required to induce moderate pain; and (2) the pain intensity induced by a predetermined level of pressure. Clinical data were also collected for the schizophrenic group.
Results: Schizophrenic patients needed less pressure (P=0.006) and a shorter duration of ischemia (P<0.001) than controls to record moderate pain, and they felt more pain from a fixed pressure stimulus (P<0.001). Pain histories for the previous 6 months and the heart rate variations that occurred during the tests did not differ between the groups. Pain responses were unrelated to the clinical characteristics of the schizophrenic patients, although hallucination production correlated with the pain felt during the fixed pressure test.
Discussion: Under these conditions, schizophrenic patients were hypersensitive to pain induction compared with normal individuals. The hypoalgesia typically associated with schizophrenic patients may correspond to fewer than normal reports of pain, rather than to impaired sensations of pain. This should be taken into account during routine medical practice.