Background: Retrograde amnesia is the most persistent cognitive adverse effect of electroconvulsive therapy (ECT); however, it is not known whether ECT has differential effects on autobiographical vs impersonal memories. This study examined the short- and long-term effects of differing forms of ECT on memory of personal and impersonal (public) events.
Methods: Fifty-five patients with major depression were randomly assigned to right unilateral (RUL) or bilateral (BL) ECT, each at either low or high electrical dosage. The Personal and Impersonal Memory Test was administered by blinded raters at baseline, during the week after ECT, and at the 2-month follow-up. Normal controls were tested at matched intervals.
Results: Shortly after ECT, patients recalled fewer events and event details than controls, with the deficits most marked for impersonal compared with personal events. Bilateral ECT caused more marked amnesia for events and details than RUL ECT, and especially for impersonal memories. These effects were independent of electrical dosage and clinical outcome. At the 2-month follow-up, patients had reduced retrograde amnesia, but continued to show deficits in recalling the occurrence of impersonal events and the details of recent impersonal events.
Conclusions: The amnestic effects of ECT are greatest and most persistent for knowledge about the world (impersonal memory,) compared with knowledge about the self (personal memory), for recent compared with distinctly remote events, and for less salient events. Bilateral ECT produces more profound amnestic effects than RUL ECT, particularly for memory of impersonal events.