Hey!
I won't tell Loki you said he has mental health issues
Loki had diabetes insipidus, which is extremely rare and went undiagnosed for his first year or so. In that time, he was in a lot of pain and would guard items and growl when you picked him up. He is also afraid of big dogs and loud noises/storms but that is probably unrelated. In any event, we have worked with him extensively and got him on medication and his behavior has gone from awful to outstanding. He knows drop, leave it (he happily drops Kongs and Bully Sticks now) and 100 other commands and he is in no way an aggressive dog. He is still a bit fearful, but rather than standing in the yard and freak out barking at another dog, he gives a quick bark and BOLTS for the front door to get back inside. He barks as he runs back to me
Anyway, his issues were never "dominance" or actual aggression but pain and fear, which is the case in a huge % of "aggression" cases. You have to find the REASON for the behavior while working to manage and improve the behavior.