Activist investor Engine Capital is pressuring Acadia Healthcare (NASDAQ:ACHC) to overhaul its board and rethink its growth strategy as the behavioral health provider grapples with federal investigations and steep share losses. In a letter to the company's board, Engine disclosed a roughly 3% stake, making it one of Acadia's 10 largest shareholders. The hedge fund urged the operator of psychiatric hospitals and recovery clinics to halt expensive new projects, review its asset portfolio, and add directors ...