Reviewing 15 studies which supplemented 2-20g of tyrosine loading during a single test session. Authors concluded that in those studies that assessed neuropsychological measures during demanding situations (stress and catecholamine depleting events,) tyrosine loading acutely counteracts the deficits that these stressors normally induce such as working memory and information processing. Unlike the previous reviews this study also assessed emotional impacts including a study that found tyrosine “increased global mood scores from baseline by 47%, whereas in the placebo condition global mood scores decreased by 136%”.
Hase A, Jung SE, aan het Rot M. Behavioral and cognitive effects of tyrosine intake in healthy human adults. Pharmacol Biochem Behav. 2015 Jun;133:1-6. doi: 10.1016/j.pbb.2015.03.008. Epub 2015 Mar 20. PMID: 25797188.