Does Mirtazapine Cause Long Term Brain Damage

I was on it for over a decade. Spent the last 7 years slowly tapering. I'm finally off, broke out in hives because apparently it's a pretty powerful antihistamine and itchiness can be a withdrawl symptom. I went from 1.25 mg to zero and it hit me so unbelievably hard. If such a small reduction can make me have all the symptoms I have had the last 10 days & hives I just wonder what this has done to my brain. Will I have a lower ability to create and recycle my neurotransmitters from here on out? Like how can I ever really know going forward if depression or anxiety is "natural" or because I robbed my brain of the ability to create it's own healthy balanced environment. I have developed debilitating chronic fatigue in the last 7 years and i feel like mirtazapine caused it.