Repeated-measures MANOVAs were performed with within-subject factors of treatment phase (placebo/glycine) and week within treatment phase (0, 2, 4, and 6 weeks). Highly significant, large effect size treatment effects were observed for negative and cognitive symptoms as well as for depression (Table 3). Glycine treatment led to a highly significant 30%±16% (95% CI, 26%-41%) decline in negative symptoms (t=9.23, df=18,P<.001), whereas no significant change in negative symptoms was observed during placebo treatment (Figure 1). Cognitive symptoms (t=6.15, df=18, P<.001) and depression (t=3.6,df=18, P<.01) improved by 16%±11% (95% CI, 10%-21%) and 17%±21% (95% CI, 6%-27%), respectively, during treatment with glycine but not placebo. The treatment × time interaction remained significant, with large effect sizes for negative (F3,13=l3.3, P<.001, f=0.75) and cognitive symptoms (F3,13=3.8, P<.05, f=0.5), even following covariation for changes in depressive symptoms. Positive symptoms showed a significant 12%±20% (95% CI, 2%-20%) reduction during glycine treatment (t=2.80, df=18, P<.02) and no significant change during placebo treatment. However, for positive symptoms, the treatment × time interaction was not significant (Table 3).