According to a recent article, since the 1980s, the percentage of American adults who say they’re lonely has doubled from 20 percent to 40 percent. As U.S. Surgeon General Vivek Murthy has often said, cancer and obesity aren’t the country’s biggest health issues — it’s loneliness and isolation. Social isolation has even been linked to strokes and the progression of Alzheimer’s disease.

Morning Shift talks to Drs. Richard Schwartz and Jacqueline Olds about what makes someone lonely and what the fine line is between blissful solitude and harmful isolation.