The toll a year of loneliness, stress, fear, trauma, and loss takes on the structure and function of the brain — Sandro Galea, MD, is a physician and epidemiologist who knows trauma: He has studied people’s mental health in the aftermath of, among other earth-shattering events, 9/11, hurricanes, and civil unrest. In March and April 2020, the Boston University School of Public Health dean conducted one of the first mental health…