BMC Public Health BioMed Central Research article Females do not have more injury road accidents on Friday the 13th Igor Radun and Heikki Summala* Open Access Address: Traffic Research Unit, Department of Psychology, University of Helsinki, PO Box 9, 00014 Helsinki, Finland Email: Igor Radun - igor.radun@helsinki.fi; Heikki Summala* - heikki.summala@helsinki.fi * Corresponding author Published: 16 November 2004 BMC Public Health 2004, 4:54 doi:10.1186/1471-2458-4-54 This article is available from: http://www.biomedcentral.com/1471-2458/4/54 Received: 14 July 2004 Accepted: 16 November 2004 © 2004 Radun and Summala; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: This study reinvestigated the recent finding that females – but not males – die in traffic accidents on Friday the 13th more often than on other Fridays (Näyhä S: Traffic deaths and superstition on Friday the 13th. Am J Psychiatry 2002, 159: 2110–2111). The current study used matched setting and injury accident data base that is more numerous than fatality data. If such an effect would be caused by impaired psychic and psychomotor functioning due to more frequent anxiety among women, it should also appear in injury crashes. Methods: We used the national Finnish road accident database for 1989–2002. To control seasonal variation, 21 Fridays the 13th were compared in a matched design to previous and following Fridays, excluding all holidays, on number of accidents, male/female responsibility for accidents, and the number of dead, injured and overall number of active participants (drivers, pedestrians and bicyclists) as a consequence of the accident. Results: There were no significant differences in any examined aspect of road injury accidents among the three Fridays, either in females or males. Women were not overrepresented in crashes that occurred on Fridays 13th. Conclusion: There is no consistent evidence for females having more road traffic crashes on Fridays the 13th, based on deaths or road accident statistics. However, this does not imply a non- existent effect of superstition related anxiety on accident risk as no exposure-to-risk data are available. People who are anxious of "Black Friday" may stay home, or at least avoid driving a car. Background One widely spread superstition is that Friday the 13th brings bad luck. However, the few studies published on human behaviour and its consequences on that day show inconsistent results, whether they be on economic behav- iour [1-3] or health risks [4-6]. A recent nationwide study by Näyhä [7] on the 1971–97 death statistics in Finland found that men's deaths did not increase on Friday the 13th but females' did by a factor of 1.61, and by 1.63 when adjusted for age, time period, temperature, and extra Poisson variation. The author's conclusion was that Friday the 13th may be a dangerous day for some women, presumably because of anxiety from superstition and, possibly, anxiolytic medications. This interpretation is not without problems. First, although the author repeatedly refers to driving, it should be noted that he also included water and air traffic acci- dents. Secondly, as the author pointed out himself, his data included passengers killed in accidents, who typically have no control on the task. Impaired psychic and psycho- motor functioning due to anxiety, which could indeed be Page 1 of 4 (page number not for citation purposes)