Meta-analytical approach to reconciling discrepancies in efficacy between bilateral and unilateral electroconvulsive therapy

A review of the literature assessing the efficacy of bilateral compared to nondominant unilateral ECT was conducted using a quantitative review procedure-meta-analysis. The results supported conventional reviews that concluded that there is no difference in outcome between bilateral and unilateral ECT. Meta-analysis also allowed an evaluation of the effects of 11 variables that span: (a) research methodology, (b) technique, (c) patient demographics, and (d) operational dimensions that have been proposed to mediate results of studies that found an advantage for bilateral over unilateral ECT. Of these variables, shorter interelectrode distance and the assessment of outcome after a fixed number of treatments (e.g., five or six ECT) rather than after completion of the full ECT course were significantly related to studies reporting a clinical advantage for bilateral ECT, and together, both accounted for 45% of the variance across studies. Although weaker effects of unilateral ECT due to shorter interelectrode distances may be related to seizure threshold, assessment after a fixed number of treatments may be related to failure to monitor seizure length.