Dissociation is a hidden mental illness in most cases because the dysfunctional family promotes, through ignorance, the mental illness. In my case it was ignorance not maliciousness. Except, my brother's abuse was maliciousness. My parents had no parenting skills and my Mom actually had very bad ideas in her head about parenting toddlers. She never considered her toddler's emotional and psychological welfare!!! So all her children were emotionally traumatized by the age of three. I got it worse because my Brother was allowed to abuse me to vent his problems. Mom believed that sibling bullying or hazing was normal.

But, if you develop a dissociative disorder late in life it only means that the mental illness had been hidden during your childhood. The child cannot deal with the insanity of the dysfunctional family. The family that traumatizes a toddler, as in my case, has no empathy for the toddler's feelings and emotions. Also dysfunctional families lack any sane communication skills. They generally do not communicate with the child enough to recognize memory problems or amnesia which is occurring all throughout childhood.

You do not develop a dissociative disorder late in life. It just was hidden until something triggered the symptoms to become obvious.