I freakin love l-theanine.
I take 100mg capsules 4-5 times a day (Every 3 to 4 hours)
I also take a 200mg capsule before bed.
Ever since my doctor wanted me off olanzapine (I am now on Lurasidone) I have had anxiety and agitation, like it can get really bad, the agitation is simply awful, I suffer bad. I take l-theanine and within 1/2 hour I feel so much better. It is quick acting. I use the NOW brand.
I am also on 1.5mg/night of clonazepam for sleep.
Here is an article about l-thenaine and schizophrenia: L-theanine is Effective in Lessening Positive Symptoms, and improving Sleep Quality in patients with schizophrenia
I can’t sing the praises of l-theanine loud enough, but that is just me, everyone is different. others may find it useless.
If I am feeling completely fine, and I take one, I don’t notice any effect, but when I feel like sh*t (anxiety and agitation) and I take one I feel better.