Unilateral Electroconvulsive Therapy: Its Effects on Memory and its Therapeutic Efficacy

¹ Institute of Experimental Psychology, University of Oxford
² M.R.C. Clinic Research Fellow, Department of Mental Health, University of Aberdeen

A comparative investigation of unilateral and bilateral E.C.T. was carried out in which the memory-disturbing effects and the therapeutic efficacy of the two forms of treatment were assessed. The trial included a total of 102 patients suffering from depressive illness, of whom 50 received courses of unilateral and 52 courses of bilateral E.C.T. Patients were randomly assigned to each treatment group.

Memory tests were given to 71 patients (35 unilateral, 36 bilateral), each patient participating in two of the four tests in the series. The tests involved the recognition of stimulus items presented either a few minutes before or one hour or two hours after the administration of single treatments. Scores obtained in these experimental tests were compared with scores obtained by the same subjects in parallel control tests given in the absence of E.C.T., the differences between the two scores providing a measure of impairment. The unilateral patients showed significantly less evidence of impairment than the bilateral patients; this applied to tests of both retrograde and anterograde amnesia and to tests given towards the beginning and end of a course. The acute effects of single treatments measured in these tests are considered to reflect closely the major types of memory disturbance induced by E.C.T.

An assessment of the therapeutic efficacy of the two forms of treatment was made on the basis of (i) self-administered depression rating scales completed before and after a course of treatments by 44 patients (24 unilateral, 20 bilateral); and (ii) the number of treatments received by 95 patients (48 unilateral, 47 bilateral). A separate analysis was also made of the number of treatments received by the 44 patients completing depression rating scales. The two forms of treatment were found to be equivalent, both in their effectiveness in relieving depressive symptoms and in the rapidity with which they act.

It is concluded that unilateral E.C.T. represents a valuable advance in technique, in that it demonstrably reduces the incidence and severity of memory disturbance associated with bilateral treatment, while attaining the same therapeutic results.

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