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Research Christmas 2015: Infection Control

Bloodcurdling movies and measures of coagulation: Fear Factor crossover trial

BMJ 2015; 351 doi: (Published 16 December 2015) Cite this as: BMJ 2015;351:h6367
  1. Banne Nemeth, medical doctor1 2,
  2. Luuk J J Scheres, medical doctor1 3,
  3. Willem M Lijfering, postdoctoral researcher1,
  4. Frits R Rosendaal, professor of clinical epidemiology1 4
  1. 1Department of Clinical Epidemiology, Leiden University Medical Centre, 2300 RC, Leiden, Netherlands
  2. 2Department of Orthopaedic Surgery, Leiden University Medical Centre, Leiden, Netherlands
  3. 3Department of Vascular Medicine, Academic Medical Centre, Amsterdam, Netherlands
  4. 4Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Centre, Leiden, Netherlands
  1. Correspondence to: F R Rosendaal f.r.rosendaal{at}
  • Accepted 13 November 2015


Objective To assess whether, as has been hypothesised since medieval times, acute fear can curdle blood.

Design Crossover trial.

Setting Main meeting room of Leiden University’s Department of Clinical Epidemiology, the Netherlands, converted to a makeshift cinema.

Participants 24 healthy volunteers aged ≤30 years recruited among students, alumni, and employees of the Leiden University Medical Center: 14 were assigned to watch a frightening (horror) movie followed by a non-threatening (educational) movie and 10 to watch the movies in reverse order. The movies were viewed more than a week apart at the same time of day and both lasted approximately 90 minutes.

Main outcome measures The primary outcome measures were markers, or “fear factors” of coagulation activity: blood coagulant factor VIII, D-dimer, thrombin-antithrombin complexes, and prothrombin fragments 1+2. The secondary outcome was participant reported fear experienced during each movie using a visual analogue fear scale.

Results All participants completed the study. The horror movie was perceived to be more frightening than the educational movie on a visual analogue fear scale (mean difference 5.4, 95% confidence interval 4.7 to 6.1). The difference in factor VIII levels before and after watching the movies was higher for the horror movie than for the educational movie (mean difference of differences 11.1 IU/dL (111 IU/L), 95% confidence interval 1.2 to 21.0 IU/dL). The effect of either movie on levels of thrombin-antithrombin complexes, D-dimer, and prothrombin fragments 1+2 did not differ.

Conclusion Frightening (in this case, horror) movies are associated with an increase of blood coagulant factor VIII without actual thrombin formation in young and healthy adults.

Trial registration NCT02601053.


  • We thank Nine Nemeth, Maaike Hermans, and Liesbeth Willems of Brilman-Tuinhof de Moed for their help with blood collection; Petra Noordijk, Annelies Hoenderdos, and Lejla Mahic for laboratory analyses; Selina Wijbenga and Yanna van der Spek for accompanying frightened study participants; and Eva Rosendaal for her expertise in horrorology. We are especially grateful to the volunteers who took part in the study.

  • Contributors: According to good epidemiological practice, the decision of who would be first and who would be second author was made by randomisation. All authors were involved in the study design, study conduct, data analysis, and revision of the manuscript. All authors read and approved the final manuscript and are guarantors of the paper.

  • Funding: This study was sponsored by the Department of Clinical Epidemiology, Leiden University Medical Center.

  • Competing interest: All authors have completed the ICMJE uniform disclosure form at and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the medical ethics committee of Leiden University Medical Center.

  • Transparency: The guarantors affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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