Experience shows that, in many reports of health issues attributed to environmental factors received by the French Institute for Public Health Surveillance (InVS), it is necessary to understand and identify the contextual factors in order to respond most effectively. Many factors can give rise to health problems—whether real or perceived—that cannot be attributed solely to the health sector; they also stem from the social and psychosocial environment, and even the psyche. The Department of Environmental Health has undertaken to identify disciplines within the human and social sciences that could broaden its analysis. Specialists in neuropsychiatry, psychoanalysis, psychosociology, sociology, and anthropology were interviewed. The example of acute mass phenomena of unexplained origin is used as a case study to highlight the benefits of such collaborations, as these situations combine the need for scientific openness with the necessity to react and mobilize very quickly. The key findings highlight the essential nature of interdisciplinarity, the need to master methodologies, and each individual’s ability to contribute to a shared responsiveness in analyzing the initial aspects of the situation. These various points are the indispensable links for the operational implementation of collaborations, enabling a better understanding of the respective roles and responsibilities within an intervention. (R.A.)