It is not uncommon for patients with mTBI to suffer from symptoms of PTSD. The symptoms can be designated into four different groups. A clinical diagnosis of PTSD requires symptoms from all four groups to be present. This creates an overlap between PCS and PTSD symptoms in the hyperarousal symptom group, difficulty concentrating and sleeping. Studies are now showing that not there is not only an overlap between PTSD and PCS but possible an interaction. This relation can make both distresses worse.