I don't know how many people here have underlying emotional issues that they recognize as either deeply connected to their depersonalization or the root cause of it but I know this is certainly the case for me. It's taken me 31 years to realize this but I'm glad I'm at that point finally.
For me, depersonalization is deeply rooted in what's called "developmental trauma" which is trauma that occurs between the ages of 1 and 5 when 80 percent of brain development occurs. Scientists are also now realizing that "trauma" is not just something bad happening to you but can also occur when you don't get enough of something you need to survive. Essentially trauma is either too much of a bad thing or not enough of a good thing. The younger this occurs in childhood the more widespread the effects.
What I've realized in dealing with two severe episodes of depersonalization in my life and recovering from both is that depersonalization is a nervous system disorder or disease. It's very much physiological. It has very specific symptoms and traits that align tightly with other central nervous system (CNS) diseases. Obviously this isn't anything revelatory but it's given me a solid foundation of knowledge and confidence to move forward in analyzing the root cause of my issues. I think it would greatly benefit our community across the globe to acknowledge this as well. Any pushback about how this is all in our heads or some kind of mood disorder only adds to the stigma and misunderstanding and prevents us from seeking the neurological support and research we need.
As for the precise topic of this post, there've been two books I've read recently that have transformed my entire view of my life and how depersonalization fits into the larger story of my health issues. One is The Pocket Guide to the Polyvagal Theory by Stephen Porges and the other is Healing Developmental Trauma by Laurence Heller and Aline LaPierre. I cannot recommend these books highly enough for this community. They have utterly transformed the way I view depersonalization and my own personal narrative.
The biggest takeaway as it relates to depersonalization from both these books is that the human nervous system basically develops a baseline view of the world as either safe or unsafe from an extremely young age and then wires the entire body to favor one or the other depending on how safe the child felt growing up. If for example you had a very loving family where nobody fought and you knew you were loved unconditionally and provided for and cared for then your nervous system developed in a healthy fashion. If however you experienced any sort of dysfunction or abuse or neglect or perhaps even a parent who didn't attend to your needs then what often results is an ongoing stress that prunes your neurons to favor a nervous system that's constantly prepared for fight, flight, freeze or feign. Essentially it's more advantageous from an evolutionary standpoint to remain prepared for danger and stress in order to survive than it is to remain calm and playful and thus offguard and prone to damage, disease or death.
As is the case with every aspect of the body, the more you use something the stronger it gets, and the nervous system is no different; however, because the brain is developing at such a rapid rate in infancy this is even more true than at any point in life. And so as children with early stress and trauma mature their nervous systems basically reflect whatever early view of the world they were bestowed being either mostly safe or dangerous, the paradox being that if you're programmed to view the world as dangerous you will grow up to constantly find threat even when there isn't any and thus continue strengthening an already overpowering "fight or flight" response. This is what many of us experience as anxiety.
So how does this relate to depersonalization?
This is where the polyvagal theory comes in. Basically polygaval theory says the main conduit of the CNS, known as the vagus nerve, is comprised of a few main systems that stem from different parts of the brain and all intermix to promote various levels of stimulus and relaxation depending on a vast array of environmental signals and social circumstances but that the root of everything is safety. As long as mammals get signals from their environment that their lives are not in danger they can really give their nervous system a go for all sorts of activities including sex, play, socialization, sleep, feeding, you name it. But if they feel threatened in some way a whole different set of nervous system wiring kicks in and won't let go until it again gets signals it's safe. But the key here is that though there's overlap with the wiring, these two systems cannot be fundamentally active at the same time in equal proportion. Evolution designed our nervous system to either heal, grow and thrive or channel all our biological recourses into staying alive and escaping danger via fight, flight, freeze or feign. So while you may be anxious as hell and still talk to people in an entirely safe environment, the fact remains your body feels unsafe and thus so does your nervous system, which is really all that matters.
My hypothesis about the root cause of depersonalization, and one I'd argue is fairly well supported by the polyvagal theory, is that some aspect of the fight, flight, freeze or feign nervous system is essentially permanently frozen. To some degree either an event or a long string of powerful events were deemed by the body so dangerous that the "rest and digest" aspect of our nervous system was completely severed, perhaps through neuronal excitotoxicity, perhaps through some kind of hormonal flooding, who knows. All that matters is that we are essentially stuck in "fight of flight." This is also the case with those suffering from PTSD which is why the symptoms of both conditions are so similar in so many ways.
I've corresponded with Dr. Porges about the precise biological mechanism by which this frozen state occurs and though he couldn't give me an exact explanation of what's going on at the cellular level what he did say is the nervous system has to get actual cues from the outside environment that it's once again safe so as to move away from being stuck in a state of anxiety. However this isn't quite as easy as it sounds. You can't, for example, just sit in your room where it's supposedly safe and expect your nervous system to recalibrate. There are actually specific sound and light frequencies that move your nervous system towards a state of safety and artificial light and sound from electronics actually trigger your nervous system to feel threat, which is why people with depersonalization can't stand fluorescent lighting for example. Things like talk therapy, singing, meditation, human touch, active listening, yoga and basic eye contact are all examples of environmental cues our nervous systems deem as safe and that can move you out of a frozen dissociated state. But to truly make the transition from being frozen in dissociation (as many here are) to a state of flow and health and normalcy seems to require lots and lots of little repeated cues of safety. In short, there's no single "cure" for depersonalization, though there may be in the future.
Anyway, this is just a very basic outline of all this stuff. I'd really encourage anyone with this condition to read up on polyvagal theory and developmental trauma as they're both intricately related and cover extensive scientific ground on depersonalization and related dissociative states. Nobody has the precise mechanistic answers for depersonalization quite yet but in reading up on this material you should be able to get a pretty good grasp at the general direction this is moving towards.