Pain thresholds as a putative functional test for cerebral laterality in major depressive disorder and panic disorder

Both major depressive disorder (MDD) and panic disorder (PD) exhibit an illness-related functional cerebral laterality with a frontal right/left asymmetry. Using experimental pain lateralization as a putative indicator of functional cerebral laterality, we assessed body side differences in pressure, cold and heat pain thresholds in patients with MDD and PD as well as in healthy control subjects (HC). To control for an attentional bias in perception, reaction times for selective attention were also measured for both visual fields.

21 inpatients with MDD, 21 inpatients with PD (DSM-IV diagnosis) and 20 HC subjects, all right-handed, were investigated drug free. Pain thresholds for pressure, cold and heat were assessed at the right and left forearm or hand. A neuropsychological standard test was used to measure selective attention (signal detection, Wiener Testsystem), which allows for the discrimination between left and right visual field stimulus processing.

In all participants, a left-sided increased pain sensitivity could be verified by using pressure pain, but not by thermal pain (cold, heat). The diagnosis of MDD or PD had no influence on pain threshold lateralization. There were no differences in reaction times of selective attention between the groups of patients and the HC. Neither did stimulus presentation in the left or right visual field affect reaction time differently.

Body side asymmetry of pain perception was only found for pressure pain targeting mainly deep tissue (muscle) nociception. This asymmetry, however, cannot be regarded as an indicator of a pathological functional cerebral laterality in MDD and PD.