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Associate Analysts


Marie Brethous is an Associate Analyst in charge of the Transatlantic Relations and EU-NATO affairs portfolio at the EU Institute for Security Studies (EUISS). She specialises in security and defence policy analysis, with a focus on the international security community.

Marie formerly worked at NATO in the Political Affairs and Security Policy (PASP) division, where she analysed political and policy developments in NATO partner countries in Western Europe as well as the Black Sea and South Caucasus regions.

Her prior experience also includes EU Government Affairs at Siemens AG, Transatlantic Relations at the German Marshall Fund of the United States (GMF) and policy development for DG EXPO at the European Parliament.

She is a member of Women in international Security (WiiS) since 2018, and a co-organiser of the upcoming 2021/2022 WiiS Mentoring Programme - a professional development scheme for women active in the fields of international relations, security and defence.

Marie holds a postgraduate degree in European Studies with a concentration in European External Relations from KU Leuven (Belgium), a graduate degree in European Studies from Maastricht University (the Netherlands) and studied Political Science at the Ludwig-Maximilians-Universität in Munich (Germany).

Viola Dreikhausen is an Associate Analyst at the EUISS, where she is responsible for the Institute’s portfolio on Conflict Research. In her capacity as editor of the EUISS Conflict Series, her thematic focus spans the prevention, onset, evolution and resolution of conflict. In addition, Viola conducts research and analyses on the future of conflict and related developments of interest to the European Union.

Prior to joining the EUISS, Viola held positions with the European University Institute, the United Nations University, the University of Lucerne, and the German Parliament. She read for a Master’s degree in Global Governance and Diplomacy at the University of Oxford and is currently completing a doctoral degree in affiliation with the European University Institute.

Katariina Mustasilta was a Senior Associate Analyst dealing with conflict research at the EUISS from May 2019 to February 2021. Her research applied both quantitative and qualitative methods to study the drivers of countries’ internal conflicts and how to prevent violent escalation, the dynamics of civil resistance, and local peace and conflict dynamics. She was the Editor of the EUISS Conflict Series.


Yana Popkostova is an Associate Analyst at EUISS since September, 2021. Responsible for the environmental security portfolio, she investigates the compound security challenges posed by climate change, environmental degradation, and ecosystems depletion, focusing on mechanisms to mitigate and prevent impacts on European security and foreign policy.

Yana is a geopolitics of energy expert. She has established record of engagement on geopolitical, governance and commodities volatility. Her work at the energy-climate-geopolitics nexus has been featured in edited volumes, expert publications, and high-level industry events.

Yana is the founder of the European Centre for Energy and Geopolitical Analysis, an Advisory Board Member of the World Energy & Meteorology Council, and a Trilemma expert at the World Energy Council.

Prior experience includes the European Parliament, the European Climate Foundation, and as an expert reviewer for the IPCC 1.5 ̊C report. She was an inaugural recipient of the EUI Policy Leaders Fellowship.

Yana holds a postgraduate degree from the London School of Economics (LSE).

Clara Portela was a Senior Associate Analyst at the EUISS from 2019 to June 2021, having previously served as a full-time faculty member in Political Science at the University of Valencia (Spain) and Singapore Management University (Singapore). Her research focuses on arms control, non-proliferation and disarmament, as well as on multilateral sanctions policies. She holds a PhD from the European University Institute in Florence and an MA from the Free University of Berlin, and she is the recipient of the THESEUS Award for Promising Research on European Integration. Clara Portela has been a Visiting Professor at the OSCE Academy in Bishkek, the College of Europe, and the University of Innsbruck, and has held visiting positions with the University of London’s Human Rights Consortium (UK), Carleton University (Canada), the Institut d’Etudes Politiques de Grenoble (France), and Monash University (Australia).