Dragged down by negative returns for shares of Home Depot and UnitedHealth, the Dow Jones Industrial Average is falling Thursday morning.

UnitedHealth shares slid in recent trading Thursday after tumbling Wednesday amid worries about potential cuts to Medicare, and a report accusing the insurer of paying secret bonuses to nursing homes.

Health-care companies fell as concerns about UnitedHealth Group persisted. UnitedHealth Group shares fell by more than 5% after analysts at brokerage HSBC warned that, even after a plunge in the stock ...