Elsevier

Psychiatry Research

Volume 157, Issues 1–3, 15 January 2008, Pages 139-146
Psychiatry Research

Reduction in the suicide rate during Advent—a time series analysis

https://doi.org/10.1016/j.psychres.2006.07.014Get rights and content

Abstract

Research has shown that there are different seasonal effects in suicide. The aim of this study is to demonstrate that the decrease in suicide rate at the end of the year is extended over the last weeks of the year and represents a specific type of seasonal effect. Suicide data were extracted from individual records of the Swiss mortality statistics, 1969–2003. The data were aggregated to daily frequencies of suicide across the year. Specifically, the period October–February was examined using time-series analysis, i.e., the Box–Jenkins approach with intervention models. The time series models require a step function to account for the gradual drop in suicide frequencies in December. The decrease in suicide frequencies includes the whole Advent and is accentuated at Christmas. After the New Year, there is a sharp recovery in men's suicide rate but not in women's. The reduction in the suicide rate during the last weeks of the year exceeds the well-recognised effect of reduced rates on major public holidays. It involves valuable challenges for suicide prevention such as timing of campaigns and enhancement of social networks.

Introduction

Research and administrative statistics from the 19th century onwards have shown that suicide frequency peaks in the late spring and summer months and is least frequent during the winter (Kevan, 1980, Massing and Angermeyer, 1985). These well-known seasonal fluctuations are superimposed by additional temporal fluctuations such as the drop in suicides around major public holidays such as Christmas and New Year's eve (Phillips and Wills, 1987, Jessen and Jensen, 1999). Recent descriptive analyses have suggested that the decrease in suicide frequencies in December is not restricted to Christmas and New Year's Eve but extends across the whole Advent season and represents a specific type of seasonal effect (Ajdacic-Gross et al., 2003). This study aims to provide more detailed evidence on this phenomenon using intervention models within a Box–Jenkins modelling framework.

Section snippets

Methods

These analyses rely on suicide data extracted from computerised records of Swiss mortality statistics (Minder and Zingg, 1989). The individual records cover the period 1969–2003. Switzerland used the ICD8 coding system until 1994 and then switched to ICD10 coding in 1995. Suicide comprised the ICD8 codes 950–959 and the ICD10 codes X60–X84, respectively. Suicide is regularly registered as the main cause of death. The 35-year period included 49,763 suicides—35,079 (70.5%) men and 14,684 (29.5%)

Results

Aggregated daily frequencies of suicide between October and February are depicted in Fig. 1 (men) and Fig. 2 (women). In an eagle-eye perspective, there is a decline of suicide frequencies towards the end of the year, which is particularly clear in the men's series. The decline in the men's series is followed by a strong upswing in the first part of January. Moreover, Christmas Eve (women) and Christmas Day (men) show particularly low frequencies of suicide.

The ARIMA analyses of men's and

Discussion

Many lay persons tend to believe that suicide is most frequent in winter months, notably in December (Granberg and Westerberg, 1999). Empirical research contradicts this notion. It has been shown consistently for more than 100 years that suicide is lowest in winter and highest in the spring and summer months (Durkheim, 2002/1897). December has been the least favored month for suicide for most of the time for which we have data (Ajdacic-Gross et al., 2005). While the amplitude of seasonality has

Conclusion

Despite these limitations, the decline in suicides during the Advent season in Switzerland is striking and hints at the potential for suicide prevention. Furthermore, it indicates that a combination of preventive features (social networks, time-related landmarks) may be distinctly more effective than the additive effect of any specific preventive strategy alone. Advent presents a renewed opportunity for suicide prevention every year.

Acknowledgment

The data were extracted from the Swiss mortality records with the authorization granted by the Swiss Federal Statistical Office in Neuchâtel, Switzerland.

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