The influence of electroconvulsive therapy on pain threshold and pain tolerance in major depression patients before, during and after treatment

Despite the findings that pain and depression are not always directly linked, enough evidence suggest that a complex relationship between pain and depression exists. Using an electronic pressure algometer placed on the sternum, the changes in pressure pain threshold (PPThr) and pressure pain tolerance (PPTol) were evaluated in 19 patients affected by refractory major depression without psychotic features, throughout a full course of electroconvulsive therapy (ECT) treatment. Measurements were done before the first treatment, after the 6th treatment and after the last treatment. After the 6th treatment, mean (±SD) PPThr increased significantly from 11.48 (±4.81) kg/cm² at baseline, to 13.7 (±5.59) kg/cm² (p = 0.0076) while PPTol did not change significantly (from 18.46 (±6.75)kg/cm² to 17.4 (±8.1) kg/cm²). At the end of the treatment course, mean (±SD) PPThr did not increase further significantly (15.06 (±5.21) kg/cm² (p = 0.0234)) while PPTol increased significantly to 21.34 (±7.8)kg/cm² (p = 0.0047). ECT's efficacy was measured with the 21-item Hamilton Rating Scale for Depression (21-HAM-D). Mean (±SD) 21-HAM-D scores decreased significantly from 30.9 (±4.15) at baseline, to 10.47 (±5.78) (p = 0.0001) after the 6th treatment, with no further significant change at the end of the treatment course (9.94 ± 3.07; p = 0.0254). Both pain threshold and pain tolerance increased following the alleviation of the depressive disorder and a possible usefulness of ECT may be postulated for treating severe, chronic pain syndromes. However, a more significant conclusion is that the increase of the PPThr noted early during ECT treatment may serve as an early outcome possible detector of ECT efficacy in depressed patients.