Can reducing remeron (mirtazapine) cause irritability. many thanks?

Possibly so, but...: When you say "reducing" Remeron, what exactly do you mean? Also, have there been any other recent changes to your other medications? You list Lexapro (escitalopram) 10 mg and Diazepam 8 mg daily. Are you on any other new medications that may not have mentioned? Any new stressors? Being more specific would assist us in providing you with a helpful answer. Do follow up with your prescriber as well. Best.