no trauma is not one of the diagnostics because dissociation (being numb spacey, feeling not connected, not having any emotional feelings for something)

that said here where I live and work in NY which is in the USA it is believed with in the mental health field that DID happens when a child under the age of 5 is extremely abused and uses their dissociation skills to create alternate personalities that hold the abuse memories/feelings/emotions that the child is unable to handle at that moment of being abused.

other locations and treatment providers may believe differently. to find out what is believed about mental disorders in your locations, contact a mental health treatment provider.. they will explain what DID is and how it is created according to your own locations/cultures understanding of the disorder.