 Recent research has suggested that using an ultrabrief pulsewidth with ECT may greatly reduce cognitive side effects, while maintaining efficacy Sackeim et al 2008. Preliminary results were positive for unilateral ECT, however, suggest that for bilateral ECT, dosing may need to be adjusted to preserve efficacy while reducing side effects. This study will examine the relative cognitive side effects and efficacy of right unilateral and bilateral ECT given with a standard pulsewidth or an ultrabrief pulsewidth. Some participants will also receive an MRI scan before and after ECT. 