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DID is on the tertiary level of structural dissociation, meaning it's the most complex form on trauma-based dissociation a person can experience, above the primary (i.e. PTSD and adjustment disorders) and secondary (i.e. C-PTSD and trauma based personality disorders) levels.
However, structural dissociation is cumulative, meaning that each level builds off of the previous level. Therefore, you can't have the tertiary level without first having the secondary level, and you can't have the secondary level without first having the primary level.
Because of that, DID includes basically all the symptoms of lower level trauma and dissociative disorders, including depersonalization and derealization, dissociative amnesia, flashbacks and nightmares, hypervigilance, identity confusion, dissociative trance and stupor, etc. Basically all the things I've listed in the original post.
Essentially what I'm saying is that if you have a trauma or dissociative disorder of any kind, you will likely have some experiences in common with DID. Alters can only form when all of these things are already experienced to a high level in the first place.
Dissociation is a spectrum, but it's much more of a linear spectrum. It's not like autism where you have a bunch of different traits that can all be experienced to different intensities without the person being more or less autistic. With dissociation, it's a straight line going from less complex dissociation to more complex dissociation, with each section of the line building off the one before it. That's why you tend to see graphics like these:
As opposed to graphics about the autism spectrum that tend to look more like this:
These "non alters" symptoms of DID are just the lower level dissociative symptoms that can lead to the development of alters when you move further along the spectrum. So if you relate to this but don't have alters, it's likely that you're just somewhere else on the line.
Of course, it's possible that you have DID and don't realize it, but just having these symptoms alone doesn't necessarily mean that's the case.