Hi, Turnip. I have psychotic depression. I don’t know if my experience will help you much or not.
A lot of the things I experience are very similar to the negative symptoms of sz. I have a couple of friends with sz that have told me that my experiences, particularly avolition but I think also alogia, seem so like negative symptoms that they suspect my diagnosis is incorrect.
But as the first article you linked indicates, I believe it’s the positive symptoms that make the difference.
I’ve had three major delusional episodes, all of them lasting years. The first was when I was a teenager, and I believed that I was a creature of darkness. I believed I was evil and caused pain and harm to everyone around me. I believed that I wasn’t worthy of being around good, decent people. I believed that people, particularly my mother, could read my thoughts, but refused to help me because I was wicked and unworthy of help.
My second period came after a three year remission, and really only ended perhaps three years ago. I believed I was somehow a criminal, that I was being monitored by the NSA, that my citizenship was going to be revoked and I wasn’t going to be allowed back into the country when I left. I thought my mail was being intercepted, my phonecalls tapped, my email monitored. I thought my landlord had put cameras in my home. I thought I was being followed around town. I mainly thought that I must have done something very wrong that I didn’t know about, but that I was going to be punished for.
My third episode came after perhaps an eight month remission. My cat died of kidney failure, but I believed I had killed him. I believed that I had poisoned him. I believed that I had let him get run over by a car. I believed I had let him get mauled by coyotes. If I heard about any action that could result in the death of a pet, I believed I had done that. I also believed that after his death, he was able to see me clearly, and he was angry at me. I believed he could come back but refused to, and so I had to prove to him that I was sorry so he would come back. I had to do this by getting another kitten and doing all the things for it that I should have done for my first cat. Over a year and a half, I probably spent $15,000 on this kitten. If anything went wrong with her, it would send me into despair, because it meant I was failing my test for my first cat. I am still coming out of this episode.
Throughout these, I’ve experienced hallucinations that I’ve never felt were real for more than a second or two. Mainly, I see lights and shadows, cats and people who aren’t there, hear very complex music that isn’t playing. These hallucinations are mainly not disturbing at all.
I’ve also had some minor delusions - that I could heal myself and other people, that I could predict injuries and illnesses in other people, that I am descended from an ancient race that ties me to living beings - animals, plants - in the natural world. None of these delusions are accompanied by any sort of need to do anything, like those with a prophet or savior delusion might experience.
The main thing about my largest delusions is that they all focused on my feelings of guilt, worthlessness and wrongness. Particularly the ones about my cat, I knew they weren’t true, but knowing that meant absolutely nothing. The fact that there is little in the way of meaningful symptoms outside of these feelings is what qualifies it as psychotic depression.
Back to negative symptoms vs depression - like I said, even my sz friends don’t see a lot of difference. I’m not sure if there’s a foolproof way to distinguish them, outside of looking at what symptoms accompany them.
Sorry if this isn’t useful to you, but I hope some of it is.