i wonder if individual differences in glutamate and dopamine can explain these reports. for many the theanine is calming, but for some, for some sometimes, it puts them on the edge. we can ask why, but few answers leap out. perhaps it is COMT-related, or it is the EGCG releasing glutamate or the caffeine and its dopamine-potentiating effects (which though not present in tea at "panic attack" levels, may still subtly predispose individuals to manifesting anxiety or neurotic symptoms)
polyphenols must be part of the cause. they are very curious compounds...
some are broken down by saliva into compounds which the liver cannot produce, so swishing your tea may product slightly different effects from chugging.
serotonergic and related activities have come to light in the last 2 years
and as madman and i posted last January, many people report anxious effects from decaff tea. so there is clearly more to the mystery here.
polyphenols, glutamate, it is not for everyone. i am drinking less tea than i used to