Studies of adults (at least 18 years) diagnosed with depression and that compared cognition before and after ECT were eligible for inclusion. Studies were required to use specific methods described in the review for diagnosis of depression and for measurement and reporting of cognitive outcomes. Studies were required to provide electrode placement details: only studies that used bitemporal, right unilateral d'Elia or Lancaster positions were included. Case reports and studies that used self-reported measures were excluded.
Mean or median age of participants in the review ranged across study groups from 31 to 80 years (where reported). Most participants had unipolar or bipolar major depression/depressive episode. Generally ECT was given two to three times a week as a brief pulse or sine wave. Total number of sessions ranged from one to 29. The anaesthetic used varied widely. The studies used 22 different standardised neuropsychological tests and reported on 24 cognitive variables. Outcomes (cognitive domains) reported in the review were: global cognitive status, processing speed, attention/working memory, verbal episodic memory, visual episodic memory, spatial problem solving, executive functioning and intellectual ability. No suitable data on retrograde memory were found.
Two reviewers independently selected the studies. Disagreements were resolved by consensus.