Statistical analysis
depressive symptoms
SECONDARY
Demographic and clinical variables were compared between groups using independent t-tests and chi-square tests. The analyses for the primary efficacy measure (global cognition) and secondary cognitive measures (verbal memory, nonverbal memory, total memory) were conducted using repeated measure ANOVA with time (baseline vs. follow-up) as a repeated measure and group (active vs. sham) as a between-subjects factor, with particular attention to the time by group interaction which would indicate differential change in cognitive performance between the two groups. Similar analyses were conducted for all individual test scores. In a supportive set of analyses we also used ANCOVA to evaluate cognitive group differences (active vs. sham) at follow-up after covarying for baseline cognitive score and change in mood symptoms (follow-up minus baseline MADRS and YMRS). For the cognitive analyses above, alpha values were adjusted based on the number of cognitive outcomes (alpha = .05/4 = .0125). The relationship between change in cognitive variables and change in mood symptoms was assessed using Spearman correlations. Time by group repeated measure analyses were also used to evaluate group differences in hippocampal volumes and in total brain grey matter volume, again with an emphasis on the group by time interactions. We evaluated the association between change in hippocampal volume and change in cognitive functioning in the active group using Pearson correlations, as well as partial correlations removing the effect of change in depressive symptoms.