 SCOTTSDALE, Ariz., Sept. 14, 2021 PRNewswire -- LifeStance Health Group, Inc. NASDAQ: LFST, one of the nations largest providers of outpatient mental health care, today announced that the Company will be added to the Russell 2000 Index, effective after the U.S. market opens on September 20, according to the preliminary list of IPO additions to the Russell indexes. 