I have suffered (and I deliberately use that word rather than experienced) from chronic depersonalization since I was a teenager. Sometimes it is worse than others and I did have a time when I was completely free of it for a summer about fifteen years ago. It is currently abating as I do more and more mindfulness meditation. That has been a surprise to me.

Depersonalization isn’t often talked about and I think that’s not because it is rare but because it so difficult to put the experience into words. I feel it as a distance between what I consider to be me, my self, and what I am sensing of myself. It is a detachment of something that should be seamless. I feel happiness and it is far away. I look down at my hands and see I am touching something and I don’t connect to that sensation. I look at something beautiful and it is as if it is happening to someone else. Things that should be familiar instead feel strange and unreal, like they are not really happening.
According to Simeon and Abugel’s Feeling Unreal, about half of adults will have had a single brief experience of depersonalization usually following something severely stressful. About one third of people who experience a life-threatening danger will have a “transient episode of depersonalization”. Approximately 10% of people who are admitted to a psychiatric hospital will also experience depersonalization.
Depersonalization is closely related to and is most likely on the same spectrum as derealization which is a detachment and distance from the outside world, i.e. other people and objects don’t look real. I used to have a lot more derealization as a teenager with only a little depersonalization but the proportions gradually swapped over as I got older.
In both depersonalization and derealization (I bet another reason these experiences aren’t talked about that much is because these are such fucking clumsy names) reality testing is intact meaning that you know that while your feelings or interactions with the outside world don’t feel entirely real, they actually are real. You know that your experience is entirely subjective. You can tell the difference. If you didn’t know that then this would be called psychosis. So it’s a pretty fundamental point, in the world of psychiatry at least.
Like all mental health symptoms or experiences, if they are intense, frequent or upsetting enough then they ‘count’ as an illness. My god, that sentence is doing a lot of heavy lifting! In the case of depersonalization, the ICD-10 uses the diagnosis depersonalization-derealization syndrome and categorises it in “mental and behavioural disorders: other neurotic disorders” and the DSM-5 uses the diagnosis depersonalization/derealization disorder and categorizes it as a type of dissociative disorder alongside dissociative identity disorder (previously called multiple personality disorder). There is some consensus and overlap about what ‘counts’ as an illness but there is a lot of unknown, grey area between the core diagnositic criteria and normal experience. This isn’t just academic. There will be people out in the world denied treatment or having their treatment changed because of these diagnostic criteria. Hopefully, clinicians are flexible enough to adapt things to suit their patients/clients but I guarantee that not all are.
I’ve asked several psychiatrists, psychiatric nurses and psychologists over the last twenty plus years about their opinions on depersonalization. I find it very hard to describe so never felt like I gave a good account of myself. My favourite psychiatrist said she thought what I was describing was a “remnant” of my psychosis. I don’t think she was right. Nurses were more likely to say the depersonalization was a manifestation of my anxiety. I think every nurse I asked said that, but I’m not sure. Other professionals talked about it as a distinct symptom that they basically didn’t know what to do with because so little is known about it. I think this is the position of my current psychiatrist. I have never been offered specific treatment for my depersonalization by any of the professionals that I’ve asked.
Many people find depersonalization and derealization hard to talk about as our language doesn’t really accommodate these experiences. You end up talking in metaphors and seeing confused expressions on the other person’s face. So my apologies if you have a confused expression on your face just now. I am still trying to organise my thoughts. Perhaps things will become more clear in the future.