Background: The clinical relationship between pain and depression has been extensively reported. The purpose of this study was to compare the cerebral blood flow (CBF) of patients with major depressive disorder (MDD) during stimulation with experimental pain tolerance or sham stimulation, before and after 2 weeks of at least partially effective antidepressant treatment (ADT), in order to determine the cerebral regions associated with pain processing in the two clinical states.
Methods: Twenty-four antidepressant-free outpatients diagnosed with MDD (DSM-IV), without any pain complaints and a basal score>or=20 points on the Hamilton Rating Scale for Depression were included. Cerebral SPECTs were performed before and after ADT. Patients were stimulated with pain pressure tolerance (PT) or sham stimulation during the radiotracer cerebral uptake time.
Results: The comparison between PT and sham stimulation before ADT showed an increase of CBF of PT stimulated patients in right temporal gyrus, left amygdale, right anterior cingulated cortex, bilateral medial frontal gyrus, bilateral insula, lingual gyrus, right precentral gyrus and left postcentral gyrus. Equal comparison after ADT showed an increase of CBF of PT stimulated patients only in left middle frontal gyrus.
Limitations: The sample includes exclusively outpatients with mild-moderate depression.
Conclusion: CBF before ADT increases in brain areas related with the affective and cognitive components of pain; in contrast, after ADT increases only in cognitive pain related areas. These results offer new avenues to investigate the cerebral substrate of the common relationship between pain and depression.