The Pentagon said Thursday that U.S. troops in Afghanistan have reported dangerously low morale, resulting in the highest rates of depression since 2005. The results do not come as a surprise to many military doctors, who say a dramatic increase in fighting has caused 70 to 80 percent of all soldiers to have witnessed the death of a friend. Nearly two thirds of troops said they had seen a roadside bomb go off within 55 yards of them. The military said it has doubled the staff of mental health staff in recent years, meaning there is one mental health-professional for every 646 soldiers. Marines reported the highest levels of stress, with nearly one in five reporting acute psychological problems.