Marianna holds degrees in medicine, health economics, and a PhD in public policy from London School of Economics and Political Science. Before joining academia in 2003 she has worked as a medical doctor in Greece, China, and the UK, as a volunteer and manager for humanitarian organizations Médecins du Monde and Médecins sans Frontiers in Iraq and Albania, and as the EU senior resident adviser to governments in transition (in Russia, Georgia and Armenia). Marianna is at present a Senior Editor for Organization Studies, and co-directs pro bono an online think tank Centre for Health and the Public Interest a charity that aims to disseminate research informing the public and policy makers (http://chpi.org.uk).

Marianna is also a Network Fellow at the Edmond J Safra Center for Ethics, Harvard University in 2014-2015.