UBC Theses and Dissertations
Electrodermal correlates of the dexamethasone suppression test in unipolar and bipolar affective disorders Williams, Karl Munro
To determine whether depressed patients who suppress normally on the Dexamethasone Suppression Test (DST) differ electrodermally from depressed patients who do not suppress normally on the DST, the skin conductance of 27 unipolar and 9 bipolar (22 DST normal and 11 DST abnormal) depresslves and 15 normal controls was monitored during two experimental conditions. In the first of these conditions, subjects were exposed to 10, 85-dB, 1,000-Hz, 1-second tones after receiving instructions that were intended to minimize electrodermal responsiveness to the stimuli. In the second experimental condition, subjects were presented with 12, 105-dB, 1,000-Hz, 1-second tones. Half of these tones had a brief gap in the middle. The subjects were required to monitor the 105-dB tones carefully and to respond to the tones that contained a gap by pressing a foot pedal. No differences in electrodermal activity between the DST normal and the DST abnormal groups were detected. Moreover, no electrodermal differences between unipolar and bipolar patients and controls were found, and there was no correlation between severity of depression (as measured by the Beck Depression Inventory) and electrodermal activity. There were also no electrodermal differences between patients who were receiving antidepressant medications when tested and those who were not receiving such medication. Patients who exhibited signs and symptoms of psychomotor retardation were observed to have significantly lower levels of tonic conductance than those patients who had no signs or symptoms of psychomotor retardation or agitation. The sexes also differed, inasmuch as males emitted fewer phasic electrodermal responses to the tones that required the subject to press the foot pedal. Moreover, males habituated to the 105-dB tones faster than did females. A number of possibilities are raised in regard to the absence of electrodermal differences between normal controls and depressives. Two principal possibilities that are discussed are the overall psychomotor status of the present sample of depressives (mostly non-retarded) and the socioeconomic and educational status of the control sample (slightly above average). It is noted that future research should focus upon reliable demonstrations of electrodermal differences between depressives and controls. It is further recommended that a heterogeneous sample of normal controls be utilized in such research and that the psychomotor status of the depressed sample be assessed carefully and possibly controlled.