Comparison of unilateral and bilateral ECT: evidence for selective memory impairment

Review of studies from the past 16 years employing quantitative measurement of memory functions before and after ECT revealed the following trends: impairment of non-verbal memory functions after less than five unilateral non-dominant ECTs; improvement of non-verbal memory functions after five or more unilateral non-dominant ECTs; no change or improvement of verbal memory functions with unilateral non-dominant ECT; consistent impairment of verbal functions with unilateral dominant ECT, and impairment of both verbal and non-verbal functions with bilateral ECT. The relative lack of impairment in memory functions with unilateral non-dominant ECT is consistent with the theory of asymmetrical hemispheric disorganization in affective disorders, and supports the choice of unilateral non-dominant ECT over bilateral or unilateral dominant ECT in the treatment of depression.