There are a lot of scientific articles and other sources of information where someone can read about this disease and its symptoms. If the affected is aware of traumatic experiences in the childhood, it's easier to conclude a possible traumatic disorder. But only a psychiatrist or psychologist can tell you the right diagnosis. The first step can be a conversation with the practitioner, who can help with further steps, like searching for the right doctor.
Personal case:
I would observe my own behavior since school. At this time I was sure to be different from all the other children at my age. I was aware of my troubled childhood and the outcome of it.