[xVedun]

Possibly something like this: Caffeine and theanine have opposed effect on attention when stressed (2017)

Based on the definition of emotional arousal, stress isn't 100% accurate, but perhaps better than aroused.

[1] https://www.thefreedictionary.com/emotional+arousal

[chalst]

That theanine has a beneficial effect on stress, via cortisol suppression, is a long-standing hypothesis. That it has other effects under the article's umbrella term of "emotional arousal" is one of the interesting novelties of the article for me.

Too late to edit the title now, but for the benefit of next time, I'm still interested in suggestions.