Understanding weekly cycles in suicide: an analysis of Austrian and Swiss data over 40 years.
BACKGROUND
Seasonal as well as weekly cycles in suicide have been described, replicated and poorly understood for a long time. In Western countries, suicides are typically least frequent on weekends and most frequent on Mondays and Tuesdays. To improve understanding of this phenomenon a strategy is required which focuses on anomalous findings beyond the regular patterns. Here, we focused on instances where the weekly suicide patterns disappear or are interrupted.


METHODS
We used data from Swiss and Austrian mortality statistics for the periods 1969-2010 and 1970-2010, respectively. First, the data were cross-tabulated by days of the week and the available socio-demographic information (sex, age, religious affiliation and region). Second, time series of cumulated daily frequencies of suicide were analysed by seasonal Autoregressive Integrated Moving Average (ARIMA) models which included intervention effects accounting for Easter and Pentecost (Whit) holidays.


RESULTS
First, the cross tabulations showed that weekly cycles may be smoothed above all in young persons and smoothed in drowning, jumping and car gas exhaustion suicides. Second, the ARIMA analyses displayed occasional preventive effects for holidays Saturdays and Sundays, and more systematic effects for holiday Mondays. There were no after effects on Tuesdays following holiday Mondays.


CONCLUSIONS
In general, the weekend dip and the Monday backlog effect in suicide show striking similarities to the Advent season effect and are interpretable within the same template. The turning points between low and high frequencies possibly provide promising frames for the timing of prevention activities.
Department of Psychiatry,Psychotherapy and Psychosomatics,Zurich University Hospital for Psychiatry, University of Zurich,Zürich,Switzerland.
V
V
Ajdacic-Gross
Department of Basic Psychological Research and Research Methods,School of Psychology,University of Vienna,Vienna,Austria.
U S
US
Tran
Institute of Social and Preventive Medicine,University of Zurich,Zürich,Switzerland.
M
M
Bopp
Department of General Practice and Family Medicine,Center for Public Health,Medical University of Vienna,Vienna,Austria.
G
G
Sonneck
Department of General Practice and Family Medicine,Center for Public Health,Medical University of Vienna,Vienna,Austria.
T
T
Niederkrotenthaler
Department of Psychoanalysis and Psychotherapy,Medical University of Vienna,Vienna,Austria.
N D
ND
Kapusta
Department of Psychiatry,Psychotherapy and Psychosomatics,Zurich University Hospital for Psychiatry, University of Zurich,Zürich,Switzerland.
W
W
Rössler
Department of Psychiatry,Psychotherapy and Psychosomatics,Zurich University Hospital for Psychiatry, University of Zurich,Zürich,Switzerland.
E
E
Seifritz
Institute of Social and Preventive Medicine,University of Zurich,Zürich,Switzerland.
M
M
Voracek
Cycles; holidays; season; suicide; time series