Forest Plots Comparing Theanine Plus Caffeine With Placebo for Alertness in the First Hour (A) and Second Hour (B) After Intake, and Overall Mood in the Second Hour (C). The prediction intervals (PI) were calculated using τ² which was 0.25, 0.12, 0.00 for plots A, B, and C, respectively. Abbreviations: C, caffeine; n, study sample size; P, placebo; PI, prediction interval; REML, restricted maximum likelihood; SMD, standardized mean difference; T, theanine.