In the paper published in the May issue of this journal, Carder et al1 put forward a new and original hypothesis, derived from the symmetrical evolution observed between mental ill-health and musculoskeletal disorders (MSDs) among UK workers in general, and healthcare workers more specifically. The authors propose that there might be ‘a shift in the presentation of ill health from a physical to a psychological perspective’. Could, to some extent, these relatively broad medical categories of MSD and mental ill-health, express in another way distress experienced at work? This new interesting hypothesis, in turn, generates questions related to what occupational surveillance schemes really measure about a complex phenomenon.

First, this article is based on the analysis of longitudinal data produced by a well-designed scheme of medical reporting (either by general practitioners or specialist physicians), namely, the ‘THOR’ system, a well-known surveillance scheme. The authors have demonstrated the robustness of their data, as for instance, when they were able to identify the effects on disease incidence of specific European Union regulations focused on prevention (eg, the decrease …