Deliberate self-harm and public holidays: is there a link?

It has previously been reported [Davenport & Birtle, 1990] that there is a positive association between nonfatal deliberate self-harm in adolescents and emotionally charged festivals, such as St Valentine's Day and Christmas Day. We studied all cases of nonfatal deliberate self-harm presenting to three Central London hospitals on St Valentine's Day and Christmas Day and on two control dates, between 1983 and 1989. No association was found between cases of deliberate self-harm and St Valentine's Day, but a negative association was found with Christmas Day.