It could be other things though. Perhaps those that think they are going to die have reacted badly to injuries in the past, they are subconsciously aware that the injury is more serious to them than someone else (or that the injury is more serious than it seems). A over the top example is people that eat peanuts and think they are going to die are more likely to die and instead of attributing this to them having a deadly allergy saying it's because they thought they were going to die.