Halloween is associated with ghouls, death, witches, zombies, and all sorts of other “negative” images. Although most Americans enjoy celebrating Halloween, it has a stereotype of being the creepiest and darkest of US holidays. One might say that Valentine’s Day is the antithesis of Halloween. Valentine’s Day is associated with love, cupid, flowers, and hearts. Culturally, we associate specific meanings and feelings to holidays and these cultural stereotypes can actually influence human physical functions.
But how strong are these holiday stereotypes? Are they strong enough to influence physical functions that are generally considered out of our control? Specifically, can these stereotypes influence spontaneous birth? Generally, the timing of spontaneous births – where a woman gives birth vaginally without being induced – are considered to be completely out a woman’s control. Levy et al. examined these exact questions in the October issue of Social Science and Medicine. They wondered if cultural views of holidays could impact birth rates in the United States. To answer this questions they looked at the rate of spontaneous, Cesarean section, and induced births on Valentine’s Day, on Halloween, and during the week before and after each holiday.
Valentine’s Day and Halloween were not only chosen because of the cultural meanings attributed to these holidays but also because they are widely celebrated but rarely holidays when doctors have a day-off. Levy et al. used data from birth certificates from 1996 to 2006 (the latest data that was available) for all births within the United States. The Valentine’s Day window included over 1.6 million births and the Halloween window included 1.8 million births.
The researchers used ANCOVA to compare birth rates on the holiday in question to the birth rate on non-holidays days for the week before and after the holiday. This was done for all three types of births (spontaneous, C-section, and induced). Additionally, to examine how generalizable the results were, the same analysis was repeated for birth rates for various minority groups.
Turns out, birth rates on the actual holidays differ from the surrounding non-holiday days. For Valentine’s Day, there was a statistically significant increase in spontaneous (3.6%) and C-section births (12.1%) on the actual holiday compared to neighboring non-holiday days. For Halloween, there was a statistically significant decrease in spontaneous (5.3%), C-section (16.9%), and induced (18.7%). The same trends were found for all subset, minority groups – meaning that the results are generalizable to the United States. All results were significant at a p< 0.001. See figure below for a visual of their results (and cute little icons to make the actual holidays).
So is “spontaneous” birth really spontaneous? Are women afraid to give birth on Halloween and can they somehow delay or speed up their delivery to miss the actual holiday? Do cultural conventions really influence our physical functioning? And if so, by what mechanism? Levy et al. suggest that cultural stereotypes may influence mentally and that there could be a hormonal response to our mental state that influence physical functions such as spontaneous births. Overall, the study pointed to what I feel is an important point. The culture in which we live can have significant influence on our biology and in order to best understand human physiology biocultural models should be incorporated whenever possible.
Levy BR, Chung PH, & Slade MD (2011). Influence of Valentine’s Day and Halloween on Birth Timing. Social science & medicine (1982), 73 (8), 1246-8 PMID: 21880409