The authors of this paper (BMJ 2018;360:j5745, doi:10.1136/bmj.j5745) would like to acknowledge the contributions of researchers from the Swiss Study on Subarachnoid Haemorrhage (Swiss SOS):
Bawarjan Schatlo, University Hospital Göttingen, Germany
Christian Fung, Jürgen Beck, and Andreas Raabe, Department of Neurosurgery, University Hospital Berne, University of Berne, Switzerland
Martin N Stienen, Jan-Karl Burkhardt, Emanuela Keller, and Luca Regli, Department of Neurosurgery, University Hospital Zurich and Clinical Neuroscience Center, University of Zurich, Switzerland
Serge Marbacher and Javier Fandino, Department of Neurosurgery, Kantonsspital Aarau, Switzerland
Daniel W Zumofen, Department of Neurosurgery, Department of Diagnostic and Interventional Neuroradiology Section and Department of Radiology, Basel University Hospital, Switzerland
Roy T Daniel and Rodolfo Maduri, Department of Neurosurgery, University Hospital Lausanne, Centre Hospitalier Universitaire Vaudois, Switzerland
Michel Roethlisberger and Raphael Guzman, Department of Neurosurgery, Basel University Hospital, Switzerland
Martin A Seule, Department of Neurosurgery, Kantonsspital St Gallen, Switzerland
Thomas Robert and Michael Reinert, Department of Neurosurgery, Ospedale Civico Lugano, Switzerland
Philippe Bijlenga and Karl Schaller, Department of Neurosurgery, University Hospital Geneva, Faculté de Médecine Genève, Switzerland