June 10 (Reuters) - LifeStance Health Group Inc’s shares jumped over 11% in their Nasdaq debut on Thursday, giving the therapy provider a market value of nearly $7.5 billion and underscoring demand for mental health services during the COVID-19 pandemic. The company’s stock, backed by an affiliate of buyout firm TPG, opened at $20, compared to the initial public offering price of $18 set on Wednesday. (Reporting by Noor Zainab Hussain in Bengaluru; Editing by Shailesh Kuber) Our Standards: The Thomson Reuters Trust Principles.