Controllability of an aversive stimulus in depressed patients and health controls: a study using slow brain potentials.

Slow brain potentials (CNV and PINV) were recorded from 18 patients with primary depression and 18 health controls under three experimental conditions. A short tone (S1) indicated the occurrence of an aversive tone stimulus (S2) which could not be terminated by a motor reaction in Condition 1 (C1) but was terminated in C2. In C3 the reaction time (RT) had to be faster than the shortest mean RT from C1 and C2 in order to stop the aversive stimulus. For both groups the RT decreased from C1 to C2 to C3 and the CNV increased from C2 to C3. CNV and RT did not differ between the groups in either condition. In C1 and C3 (uncontrollability and restricted control over the aversive stimulus) patients developed a marked PINV which was not observed in the control group. In view of other investigations which found a PINV in normal subjects in situations of sudden, unexpected uncontrollability, the present results demonstrate that depressed patients are more sensitive to levels and variation of uncontrollability than healthy subjects. A possible relationship to Seligman's concept of helplessness is discussed.