The study found that USASOC personnel reported clinical levels of PTSD symptoms in 12 percent of concussions from blunt trauma, 23 percent from blast trauma and 31 percent from combination blast-blunt trauma. By contrast, only 6 percent of those who experienced clinical PTSD had never been diagnosed with a concussion. PTSD reactions were more likely as concussions increased: in 22 percent of personnel after one blast concussion, 29 percent after two and 34 percent after three."The findings regarding the clinical PTSD-symptom levels highlight the importance for military medical personnel to screen for and treat PTSD as well as concussion in personnel exposed to concussions, particularly those exposed to multiple-blast traumas," said Kontos, the corresponding author on the paper. "The dose-response relationship between the number of blast concussions and residual concussion and PTSD symptoms supports the notion that exposure to blast head trauma has lingering effects."