Ptsd is characterized by sleep disturbances and repetitive nightmares.

“if you look at the diagnostic criteria for PTSD firstly you see sleep disturbance and as I said right at the top of this episode there is no major psychiatric disorder where there isn't some mention of sleep problems in its diagnostic criteria but something else was intriguing about PTSD that compelled me to think about it and then create a theory around it it's not just sleep problems it's also nightmares and specifically repetitive nightmares in fact repetitive nightmares form part of the diagnostic criteria for you to receive a diagnosis of PTSD”