Participants receiving memantine did not show a statistically or clinically significant change in MADRS scores compared to placebo , either over the entire study ( = 0.133 , favoring placebo , P = .74 ) or at study completion ( week 8 mean [ SD ] MADRS score change = -7.13 [ 6.61 ] [ memantine ] ; -7.25 [ 11.14 ] [ placebo ] ; P = .97 ) .