As reported earlier, previous MST t

As reported earlier, previous MST treatment trials have yielded variable results (e.g., Kayser et al. [10] reported a 46% remission rate and Fitzgerald et al. [11] reported a 15% remission rate). There are key differences between these trials and ours. These differences include site of stimulation (i.e., frontal versus vertex) and the number of treatments administered (up to 18 in Kayser et al. [10], up to 15 in Fitzgerald et al. [12], and up to 24 in our trial). We cannot conclude whether there are any benefits to frontal stimulation compared with vertex stimulation. By contrast, it appears that longer courses of treatment (as in both the Kayser et al. studies and our study) are associated with higher remission rates.Another limitation of our study is the consecutive (nonrandom) allocation of patients to the different frequency groups. The low and moderate frequency groups had a higher total number of antidepressant medications trials for the current episode than the high-frequency group. However, even though these differences were not significant in the protocol completers, differences in clinical outcomes between the high and low-frequency groups remained.While our overall findings suggest that MST does not affect cognitive performance, three findings survived correction for multiple comparisons. First, there were significant decreases in AMI-SF scores in all three frequency groups. The AMI-SF is the short form version of the Autobiographical Memory Interview [23]. This measure has recently been criticized due to the lack of normative data from healthy control samples or appropriately matched depressed non-ECT samples, and the absence of reliability and validity studies [29]. However, proponents of the AMI-SF have reported on its sensitivity in differentiating the effects of different forms of ECT (e.g., bitemporal versus right unilateral electrode configuration) on retrograde autobiographical amnesia (RAA). Kessler et al. [30] compared the effects of right unilateral ECT to pharmacotherapy on neurocognitive function. Pharmacotherapy alone produced a decay of autobiographical memory consistency loss of 19% on the AMI, significantly better than the ECT group of 27% consistency loss, and equivalent to the overall AMI consistency loss of 19% in our trial. Given that there is a natural and well-documented loss that characterizes normal autobiographical memory function, and that the AMI-SF is a psychometrically unsound measure, it is difficult to characterize any decreases on the AMI-SF as conclusive evidence of retrograde amnesia induced by MST. Importantly, from baseline to post-treatment, performance across all other cognitive measures remained stable without clinically meaningful changes, except there was improvement in visuospatial memory. Collectively, the unadjusted and multiple comparison adjusted findings suggests that MST is cognitively safe, which is consistent with prior research [31].