A re-examination of seasonal variation in suicides in Australia and New Zealand

Impact of the COVID-19 Pandemic on Adolescent Self-Harm: Based on a National Emergency Department Information System

Republic of Korea's suicide rate is the highest among Organization for Economic Co-operation and Development countries. In Republic of Korea, suicide is the leading cause of death among young people aged 10-19 years. This study aimed to identify changes in patients aged 10-19 years who visited the emergency department in Republic of Korea after inflicting self-harm over the past five years and to compare the situations before and after the outbreak of the COVID-19 pandemic. Analysis of government data revealed that the average daily visits per 100,000 were 6.25, 8.18, 13.26, 15.31, and 15.71 from 2016 to 2020, respectively. The study formed four groups for further analysis, with the population divided by sex and age (10-14 and 15-19 years old). The late-teenage female group showed the sharpest increase and was the only group that continued to increase. A comparison of the figures 10 months before and after the outbreak of the pandemic revealed a statistically significant increase in self-harm attempts by only the late-teenage female group. Meanwhile, visits (per day) in the male group did not increase, but the rates of death and ICU admission increased. Additional studies and preparations that account for age and sex are warranted.

Changing Seasonal Pattern of Suicides in Korea Between 2000 and 2019

OBJECTIVE

This study aimed to investigate the changing seasonal pattern of suicides in Korea between 2000 and 2019.

METHODS

We calculated a seasonal pattern of suicides between 2000 and 2019 using a non-stationary cosinor model. In addition, we estimated the effect of each month on the suicide incidence compared to a reference month, using a generalized linear model with a categorical variable of the month. Then, we visualized the rate ratio curves of suicides by gender, age group, and subperiod.

RESULTS

We observed a seasonal pattern of suicides in Korea with a spring peak and a winter trough. The seasonal ups and downs were most pronounced in suicides among the elderly ≥65 years. However, the seasonal pattern has not been consistent over the past two decades, with lowering seasonal peaks since 2012. The amplitude of seasonality was also lower in 2010-2019 than in 2000-2009.

CONCLUSION

The seasonal pattern of suicides seems to have diminished in Korea in recent years. Thus, we need further studies to investigate climatic and non-climatic factors influencing the seasonality of suicides and the consequence of the change.

Quality and quantity of serious violent suicide attempts during the COVID-19 pandemic

BACKGROUND

While repeated shutdown and lockdown measures helped contain the spread of SARS-CoV-2 during the COVID-19 pandemic, social distancing and self-isolation negatively impacted global mental health in 2020 and 2021. Although suicide rates did reportedly not increase during the first months of the pandemic, long-term data, and data on the quality of serious violent suicide attempts (SVSAs) are not available to date.

MATERIALS AND METHODS

Orthopaedic trauma patient visits to the emergency department (ED), ED trauma team activations, and SVSAs were retrospectively evaluated from January 2019 until May 2021 in four Level-I Trauma Centers in Berlin, Germany. SVSAs were assessed for suicide method, injury pattern and severity, type of treatment, and length of hospital stay.

RESULTS

Significantly fewer orthopaedic trauma patients presented to EDs during the pandemic (n = 70,271) compared to the control (n = 84,864) period (p = 0.0017). ED trauma team activation numbers remained unchanged. SVSAs (corrected for seasonality) also remained unchanged during control (n = 138) and pandemic (n = 129) periods, and no differences were observed for suicide methods, injury patterns, or length of hospital stay.

CONCLUSION

Our data emphasize that a previously reported rise in psychological stress during the COVID-19 pandemic does not coincide with increased SVSA rates or changes in quality of SVSAs.

Seasonality of Suicides among Victims Who Are under the Influence of Alcohol

Introduction: Suicide is one of the most frequent causes of death. According to the World Health Organization (WHO), each year, over eight hundred thousand people worldwide die as a result of suicide. The most common risk factors for suicide are depressive disorders and alcohol dependence. Alcohol can directly influence a decision about suicide, or be a factor facilitating this decision. The aim of the study was to analyse the seasonality of suicides among persons under the influence of alcohol. Material and Methods: Data for analysis were obtained from the Department of Forensic Medicine (DFM) of the Medical University of Warsaw. A retrospective analysis was performed on 317 victims of suicides by hanging, those which were entered into the registry of deaths kept by the DFM in the years 2009–2013. The analysis took into account the age and sex of victims, initial cause of death, date of post-mortem examination, autopsy result and alcohol concentration in the blood or muscles of the victims. Statistical analysis was performed using IBM SPSS Statistics version 20. Results: In the analysis, a spring peak of suicides was found for men, and an autumn peak was revealed for women. In addition, a significant correlation was observed between the age of victims and the concentration of alcohol; the older the victims, the higher the alcohol concentration. However, this correlation was reported only in the spring months. Conclusions: The results of the analysis seem to be consistent with seasonal patterns observed in other studies, and they indicate the occurrence of suicide seasonality. In order to improve the strategies of suicide prevention, it is necessary to identify factors which are related to the seasonal variation of suicidal behaviours, as well as to gain knowledge about the mechanisms behind this phenomenon.

Seasonal changes in suicide in South Korea, 1991 to 2015

Seasonality of suicidal behavior has been widely reported in many epidemiological studies with a well replicated suicide peak in spring followed by a trough in winter season. Research from some regions over the past few decades has shown a diminishing seasonal pattern of suicides and this introduced a new perspective on the suicide study. Data on all suicide deaths from the period 1991 to 2015 was extracted from the South Korean National Death Registration data set which was made available by Statistics Korea. Our findings confirmed a strong seasonal effect of suicides in South Korea throughout the study period and a marked diminishing pattern was observed since the period of 2006–2010. The rhythm of suicides kept changing across the time intervals with a spring peak followed by a second peak in late summer/autumn. The seasonality varied across age groups and the seasonal effect among the Korean elderly suicides was still found to be significant though a diminishing pattern was observed recently.

Springtime Peaks and Christmas Troughs: A National Longitudinal Population-Based Study into Suicide Incidence Time Trends in the Netherlands

BACKGROUND

Time trends are one of the most studied phenomena in suicide research; however, evidence for time trends in the Dutch population remains understudied. Insight into time trends can contribute to the development of effective suicide prevention strategies.

METHODS

Time trends in national daily and monthly data of 33,224 suicide events that occurred in the Netherlands from 1995 to 2015 were examined, as well as the influence of age, gender, and province, in a longitudinal population-based design with Poisson regression analyses and Bayesian change point analyses.

RESULTS

Suicide incidence among Dutch residents increased from 2007 until 2015 by 38%. Suicide rates peak in spring, up to 8% higher than in summer (p < 0.001). Suicide incidence was 42% lower at Christmas, compared to the December-average (IRR = 0.580, p < 0.001). After Christmas, a substantial increase occurred on January 1, which remained high during the first weeks of the new year. Suicide occurred more than twice as often in men than in women. For both genders, the results indicated a spring time peak in suicide incidence and a trough at Christmas. Suicide rates were highest in the elderly (age group, 80+), and no evidence was found of a differential effect by season in the age groups with regard to suicide incidence. No interaction effect was found with regard to province of residence for both season and Christmas, indicating that no evidence was found that these time trends had differential effects in the Dutch provinces in terms of suicide incidence.

CONCLUSION

Evidence was found for time trends in suicide incidence in the Netherlands. It is recommended to plan (mental) health care services to be available especially at high-risk moments, at spring time, and in the beginning of January. Further research is needed to explore the protective effect of Christmas in suicide incidence.

The effectiveness of suicide prevention programmes: urban and gender disparity in age-specific suicide rates in a Taiwanese population

OBJECTIVE

The effectiveness of suicide prevention programmes is an important issue worldwide today. The impact of urbanization and gender is controversial in suicide rates. Hence, this study adjusted on potential risk factors and secular changes for suicide rates in gender and rural/urban areas.

STUDY DESIGN

Observational study.

METHODS

A Suicide Prevention Center was established by the Executive Yuan in Taiwan in 2005 and tried to carry out suicidal intervention in the community in every city and town. There were two phases, including the first phase of the programme from 2005 to 2008, and the second phase of the programme from 2009 to 2013. The crude suicide rates data from the period of 1991-2013, which recruited nine urban and 14 rural areas in Taiwan, were extracted from the Taiwanese national mortality data file. The suicide rates in two areas of Taiwan (Taipei city and Yilan County) were further used to compare the differences between urban and rural areas.

RESULTS

The results show that unemployment increased the suicide rate in men aged 45-64 years and in women older than 65 years of age in Taiwan. High divorce and unemployment rates resulted in increased suicide rates in men in the city, whereas emotional distress was the main cause of suicides in men in rural areas. The main method of suicide was jumping from a high building for both sexes in the city, whereas drowning was the most common method of suicide for men in rural areas.

CONCLUSION

Following the intervention programme, suicide behaviour began to decrease in all urban and rural areas of Taiwan. This study showed the cumulative effect of the intervention programme in decreasing the suicide rate in Taiwan. Moreover, the gender-specific suicidal rate and disparity in suicidal methods in urban and rural areas should be considered in further preventive strategies in Taiwan.

Solar radiation increases suicide rate after adjusting for other climate factors in South Korea

OBJECTIVE

Previous studies have indicated that suicide rates have significant seasonal variations. There is seasonal discordance between temperature and solar radiation due to the monsoon season in South Korea. We investigated the seasonality of suicide and assessed its association with climate variables in South Korea.

METHOD

Suicide rates were obtained from the National Statistical Office of South Korea, and climatic data were obtained from the Korea Meteorological Administration for the period of 1992-2010. We conducted analyses using a generalized additive model (GAM). First, we explored the seasonality of suicide and climate variables such as mean temperature, daily temperature range, solar radiation, and relative humidity. Next, we identified confounding climate variables associated with suicide rate. To estimate the adjusted effect of solar radiation on the suicide rate, we investigated the confounding variables using a multivariable GAM.

RESULTS

Suicide rate showed seasonality with a pattern similar to that of solar radiation. We found that the suicide rate increased 1.008 times when solar radiation increased by 1 MJ/m² after adjusting for other confounding climate factors (P < 0.001).

CONCLUSION

Solar radiation has a significant linear relationship with suicide after adjusting for region, other climate variables, and time trends.

Biometeorological Modelling and Forecasting of Monthly Ambulance Demand for Hong Kong

Introduction

Given the aging population in Hong Kong and the ever rising demand for emergency ambulance services, this study aimed to examine the effects of seasonality and weather on the demand for emergency ambulance services in Hong Kong. The feasibility of using time series models and selected weather factors to forecast average daily ambulance demand over a month was also assessed.

Methods

Monthly statistics for ambulance demand from 1998 to 2007 were obtained for analysing the effects of seasonality and weather on the demand for emergency ambulance services in Hong Kong. The effectiveness of weather factors in forecasting ambulance demand was also examined by comparing the performance of the autoregressive integrated moving average (ARIMA) model against other commonly used models.

Results

The lowest temperatures during cooler months were found to be negatively associated with average daily ambulance demand (adj-R2=0.38), while the average amount of cloud cover and highest temperatures were found to be positively associated with average daily ambulance demand during hotter months (adj-R2=0.34). When the analysis was stratified spatially by ambulance command units, Hong Kong Island had the highest adj-R2 during cool and hot months, reported at 0.55 and 0.46 respectively. With the inclusion of average temperature, the ARIMA models outperformed other models for both short- and long-term predictions.

Conclusions

Our findings suggest that weather factors, especially temperature, are significantly related to and useful for predicting ambulance demand.

Seasonality of Suicide in Eastern Europe: A Rejoinder to Lester and Moksony

Seasonality of suicide in Hungary decreased from the 1980s to the 1990s, supporting the 2003 conclusion of Lester and Moksony. However, it was the strongest ever to be documented with contemporary suicide data, supporting the conjecture of Voracek, et al. (2002) that seasonality of suicide remains high in Eastern Europe. A new hypothesis regarding the co-occurrence of high incidence and strong seasonality of suicide is presented.

Seasonal differences in the day-of-the-week pattern of suicide in Queensland, Australia

Various temporal patterns of suicide events, according to time of day, day of week, month and season, have been identified. However, whether different dimensions of time interact has not been investigated. Using suicide data from Queensland, Australia, this study aims to verify if there is an interaction effect between seasonal and day-of-the-week distribution. Computerized suicide data from the Queensland Suicide Register for those aged 15+ years were analyzed according to date of death, age, sex and geographic location for the period 1996-2007. To examine seasonal differences in day-of-the-week pattern of suicide, Poisson regressions were used. A total of 6,555 suicides were recorded over the whole study period. Regardless of the season, male residents of Brisbane had a significantly marked day-of-the-week pattern of suicide, with higher rates between Mondays and Thursdays. When seasonal differences were considered, male residents in Brisbane showed a Monday peak in summer and a wave-shape pattern with a peak on Thursday and a nadir on Saturdays in winter. Whilst males have distinctive peaks in terms of days of the week for summer and winter, females do not show similar patterns.

Seasonality of self-destructive behaviour: seasonal variations in demographic and suicidal characteristics in Van, Turkey

OBJECTIVE

Seasonality is one of the most interesting but still elusive issue in suicide research. Linkages of seasonality in suicides to possible contributors such as gender, type of method used, and climatic factors have received attention in different cultures. We aimed at evaluating seasonal trends in suicidal behaviour according to demographic characteristics, reasons for self-destructive behaviour and means preferred in suicide.

METHODS

Our aim was to assess the seasonal variation in self-destructive behaviour in terms of completed and attempted suicides in a 3-year time period from 2008 to 2010 in Van, Turkey. A total of 1448 cases were registered over a 3-year time period in the city. Seasonal deviations in demographic characteristics, reasons for suicide, and methods of suicide were evaluated.

RESULTS

Seasonal distribution of both completed and attempted suicides by gender did not significantly deviate. On the other hand, we found a significant decline in self-destructive behaviours among those who were single and student in the spring. We found a peak in self-destructive behaviours in the autumn among Individuals who suffer from psychological problems.

CONCLUSIONS

Subjects with psychological difficulties were more prone to commit suicide in autumn. Seasonal differences in methods of suicide used by suicidal subjects were not significant.

Seasonality of suicidal behavior

A seasonal suicide peak in spring is highly replicated, but its specific cause is unknown. We reviewed the literature on suicide risk factors which can be associated with seasonal variation of suicide rates, assessing published articles from 1979 to 2011. Such risk factors include environmental determinants, including physical, chemical, and biological factors. We also summarized the influence of potential demographic and clinical characteristics such as age, gender, month of birth, socioeconomic status, methods of prior suicide attempt, and comorbid psychiatric and medical diseases. Comprehensive evaluation of risk factors which could be linked to the seasonal variation in suicide is important, not only to identify the major driving force for the seasonality of suicide, but also could lead to better suicide prevention in general.

Suicide and seasonality

OBJECTIVE

  Seasonal variation of deaths by suicide offers an important pathway in the study of possible suicide determinants of suicide and consequently suicide prevention.

METHOD

  We conducted a review of the literature on suicide seasonality, assessing articles published between 1979 and 2009.

RESULTS

  The majority of the studies confirm a peak in spring, mainly for men, older individuals, and violent methods of suicide. A secondary peak during autumn is observed. There is no common seasonality pattern for suicide methods. However, there are also certain studies that did not confirm seasonal variation. Inconsistent results with reduced, unchanged, and even increased suicide seasonality have been reported. Aspects on the association between seasonality and suicides are discussed. Except sex, age, and method of suicide, other parameters were taken into account to find more specific characteristics of seasonality in suicides as well. The influence of clinical, bioclimatic, sociodemographic as well as biological factors seems to affect the seasonal variation.

CONCLUSION

  Studies from both the Northern and the Southern hemisphere report a seasonal pattern for suicides. These studies are not only an important source of epidemiological data for suicides but also represent a global effort to uncover hidden parameters of this self-destructive behaviour.

Seasonal and socio-demographic predictors of suicide in Ireland: a 22 year study

BACKGROUND

Seasonal influences on suicide have been studied for many years with inconclusive and contradictory findings.

METHODS

Data on suicide in Ireland from 1980 to 2002 was examined to ascertain the contribution of season and demographic variables to suicide. Using Poisson regression modelling and sinusoidal analysis a small seasonal effect (7% from peak to trough) was identified but age, gender, marital status and residence were much larger contributors. The seasonal contribution increased in the latter half of the period under study. There was also a small seasonal effect for method of suicide. The suicide rate was highest in the 40-44 age group after controlling for confounders.

LIMITATIONS

Because this was an ecological study, information on other possible contributors, such as mental illness was not available.

CONCLUSIONS

These findings are discussed in light of international studies. Continuing studies are required to confirm the trend in increasing seasonality in Ireland. Since suicide is highest in those who are middle aged, preventive strategies should be directed to this group.

Seasonality of suicide in Shandong China, 1991-2009: associations with gender, age, area and methods of suicide

BACKGROUNDS

Whether suicide in China has significant seasonal variations is unclear. The aim of this study is to examine the seasonality of suicide in Shandong China and to assess the associations of suicide seasonality with gender, residence, age and methods of suicide.

METHODS

Three types of tests (Chi-square, Edwards' T and Roger's Log method) were used to detect the seasonality of the suicide data extracted from the official mortality data of Shandong Disease Surveillance Point (DSP) system. Peak/low ratios (PLRs) and 95% confidence intervals (CIs) were calculated to indicate the magnitude of seasonality.

RESULTS

A statistically significant seasonality with a single peak in suicide rates in spring and early summer, and a dip in winter was observed, which remained relatively consistent over years. Regardless of gender, suicide seasonality was more pronounced in rural areas, younger age groups and for non-violent methods, in particular, self-poisoning by pesticide.

CONCLUSIONS

There are statistically significant seasonal variations of completed suicide for both men and women in Shandong, China. Differences exist between residence (urban/rural), age groups and suicide methods. Results appear to support a sociological explanation of suicide seasonality.

Suicide seasonality: complex demodulation as a novel approach in epidemiologic analysis

Background

Seasonality of suicides is well-known and nearly ubiquitous, but recent evidence showed inconsistent patterns of decreasing or increasing seasonality in different countries. Furthermore, strength of seasonality was hypothesized to be associated with suicide prevalence. This study aimed at pointing out methodological difficulties in examining changes in suicide seasonality.

Methododology/Principal Findings

The present study examines the hypothesis of decreasing seasonality with a superior method that allows continuous modeling of seasonality. Suicides in Austria (1970–2008, N = 67,741) were analyzed with complex demodulation, a local (point-in-time specific) version of harmonic analysis. This avoids the need to arbitrarily split the time series, as is common practice in the field of suicide seasonality research, and facilitates incorporating the association with suicide prevalence. Regression models were used to assess time trends and association of amplitude and absolute suicide numbers. Results showed that strength of seasonality was associated with absolute suicide numbers, and that strength of seasonality was stable during the study period when this association was taken into account.

Conclusion/Significance

Continuous modeling of suicide seasonality with complex demodulation avoids spurious findings that can result when time series are segmented and analyzed piecewise or when the association with suicide prevalence is disregarded.

Seasonality in suicide--a review and search of new concepts for explaining the heterogeneous phenomena

Seasonality is one of the oldest and most resistant-to-elucidation issues in suicide research. However, in recent years epidemiological research has yielded new results, which provide new perspectives on the matter. This qualitative review summarizes research published since the 1990 s. In particular, the focus is on studies dealing with the historical change of seasonality, cross-sectional comparisons including method-specific diversity, and the association with weather variables and other putative covariates. Recent research has shown that in Western countries the seasonality of suicide is tending to diminish and may, eventually, disappear. It can no longer be considered a universal and homogeneous phenomenon. In addition, different major seasonal cycles have now been determined which mainly depend on different suicide methods. Just as in the epidemiology of suicide methods, the (seasonal) availability and perceived adequacy of methods emerge as the major driving force beyond the seasonal phenomena in suicide.

Seasonality of suicide in Sweden: relationship with psychiatric disorder

BACKGROUND

Little is known as to whether suicide seasonality is related to psychiatric disorders affecting suicide risk/incidence. The present study aims to assess suicide seasonality patterns with regard to the history of psychiatric morbidity among suicide victims.

METHODS

The history of psychiatric inpatient diagnoses in the five years prior to suicide was identified among all suicides in Sweden from 1992 to 2003. Suicide seasonality was estimated as the relative risk of suicide during the month of highest to that in the month of lowest suicide incidence. Analyses were performed with respect to sex, suicide method and history of inpatient treatment of psychiatric disorder.

RESULTS

Among both male (n=9,902) and female (n=4,128) suicide victims, there were peaks in suicide incidence in the spring/early summer. This seasonal variation was more evident in suicide victims with a psychiatric inpatient diagnosis than in those without such a diagnosis. A seasonal variation was found in most diagnostic groups, with significant peaks in males with a history of depression and in females with a history of a neurotic, stress-related, or somatoform disorder. Overall, suicide seasonality was more evident in violent than in non-violent suicide methods.

LIMITATION

Only psychiatric disorders severe enough to require hospital admission were studied.

CONCLUSION

A history of inpatient-treated psychiatric disorder appears to be associated with an increase in suicide seasonality, especially in violent suicide methods. This increase is found in several psychiatric disorders.

Seasonality of violent suicides in the Athens greater area

The aim of the study was to ascertain suicide seasonality in the Greek population and to associate this seasonal variation with age, sex, and suicide method. Studying seasonality can be of help in establishing a public health policy, related with suicide prevention. This is an epidemiologic study based on forensic evidence. We studied the deaths caused by self-injury (trauma), namely deaths by violent suicide (not self-poisoning). Statistically significant suicide seasonality was established with a peak in May. This seasonal variation is attributed mainly to males. As for the method, suicide by hanging peaks in June and by shooting in April. It was also observed that seasonality for individuals above the age of 45 peaks in early May.

Autumn peak in shooting suicides of children and adolescents from northern Finland

Suicide is one of the leading causes of death among adolescents worldwide. Studies on the seasonal pattern of youth suicides are rare and the results are very contradictory and heterogeneous. Generally, suicide methods affect the pattern of suicide seasonality. Shooting is the most common suicide method among Finnish adolescents. We investigated whether shooting suicides of victims aged less than 18 years are correlated with a specific period of the year. Also, the seasonal pattern of shooting suicides in adolescents was compared with that of adult victims. Our data comprised 42 adolescent suicide victims and, for comparison, 1,926 adult suicide victims over the years 1988 to 2004 from Northern Finland. Of these, 59.5% (n = 25) of the adolescents and 28.8% (n = 554) of the adults had committed suicide by shooting. We observed that shooting suicides among the under-aged showed a significant peak in autumn (ratio 2.70, 95% CI: 1.97-3.42), while those of adult victims peaked in spring (ratio 1.19, 95% CI: 1.05-1.35). The monthly pattern of suicides correlated significantly with the mean duration of daily sunshine hours (trailing by 3 months) in the under-aged (r = 0.67, p = 0.016), but not in the adults (r = 0.06, p = 0.854). The role of firearm availability, psychosocial factors such as start of the school year, and some biological factors are discussed.

Seasonality of suicides with and without psychiatric illness in Denmark

This paper studied the seasonality of suicides among persons with and without psychiatric illness in Denmark from 1970 to 1999. A non-homogenous Poisson process was used to examine the data. The seasonality of suicides was shown to be associated with gender and their psychiatric histories with a declining trend of suicide incidence noted over the captured period. A mild seasonal component was reported in the period of the late 70s to early 80s (1975-1984) among females who did not have any psychiatric treatment history, while in the 80s the significant seasonality was mainly contributed by male suicides without a psychiatric history. Another mild possible invoked seasonality in the 90s was in males who suffered from psychiatric illness. The rest could be treated as random events. Apparently, the seasonality among suicides with psychiatric illness exists but its effect could vary in different periods of time and among genders in Denmark.

Suicide rates and the association with climate: a population-based study

BACKGROUND

Seasonality of suicide has been noted in several studies. A spring peak of suicide was observed, and associations between various climatic parameters and suicide have been suggested. This study sets out to verify seasonal patterns of suicide rates and to explore the association with climate in Taiwan.

METHOD

The study used a nationwide mortality database in Taiwan from January 1997 to December 2003. An autoregressive integrated moving average model was applied to examine the presence of seasonality and the association of climate with suicidal death.

RESULTS

Seasonality with a spring peak was evident in suicidal death regardless of gender or age. Ambient temperature was positively associated with suicide after adjustment for trend and seasonality.

LIMITATIONS

Misclassification and underreporting of suicidal death in the registry system might confound the results. Ecological fallacies might exist.

CONCLUSIONS

The seasonal effect on suicide is significant in Taiwan. Suicide rates may be influenced by ambient temperatures. The findings are of research interest for future studies regarding mechanisms of suicidal behavior, and also of practical interest for better timing of suicide interventions and effective preventive strategies.

Diversity and change in suicide seasonality over 125 years

BACKGROUND

Recent research has corroborated the notion that seasonality in suicide is more heterogeneous and less consistent than postulated by former scholars. This work investigates the smoothing out of suicide seasonality in Switzerland between the late 19th and the end of the 20th century. It includes analyses by region and by suicide method.

METHODS

Monthly suicide frequencies in Switzerland are available for the period 1876-2000. Data on canton/region are available for the periods 1901-1920 and 1969-2000, and data on suicide method for the periods 1881-1920 and 1969-2000. Analyses focusing on the overall change rely on data aggregated by quinquennia. The Edwards' test and the peak-low ratio were used in univariate analyses of seasonality. Putative determinants of the peak-low ratio were examined using regression analysis with cantonal data.

RESULTS

The decrease of seasonal effects in suicide applies to a period of more than 100 years in Switzerland. Big differences of seasonal effects have existed all the time with regard to specific methods and to specific regions. No seasonality was apparent in poisoning, and in Geneva and Basle City, respectively. However, the seasonal effects have been most impressive in drowning and hanging suicides, and in rural Catholic regions. In regression analysis, the decline in suicide seasonality is associated with the decline in the agricultural work force.

CONCLUSIONS

The smoothing out of suicide seasonality in Switzerland has been a continuous long term process, which probably started by the end of 19th century. Seasonal effects in suicide will probably fade away in most regions of Switzerland and in most suicide methods. This process is in parallel with the disappearance of the traditional rural society.

Seasonal changes in suicide in the United States, 1971 to 2000

The seasonality of suicides in the USA increased from the 1970s to the 1990s. A significant proportion of suicide variation due to the seasonal component has been reported. Noted increments in seasonal rhythms in the latter part of the 1980s and 1990s seem to support those of Warren, et al. but contradict the conclusions of diminishing drawn by Hakko, et al., Rhimer, et al., and Yip, et al.

Impact of case fatality on the seasonality of suicidal behaviour

A number of differences exist between the seasonality of suicide and suicidal behaviour. Case fatality is one index of the relationship between these phenomena. The purpose of this study was to use contemporaneous data to examine the impact of case fatality on the seasonality of suicidal behaviour. All deliberate self-harm (ICD9 E950-58) hospitalisations (DSH) and deaths (suicide) for 1984-93 were extracted from the Western Australia case register (N=22 883). Case fatality was calculated by method of suicide. Data were arranged in time series by standardised month according to case fatality; sex and age and analysed using spectral analysis. We found that DSH involving low case fatal methods is seasonal with a spring peak (95% confidence interval). The explained variance of the seasonal rhythm increases with age. Suicide involving high case fatal methods is not seasonal. The increase in DSH seasonality with age may be related to a parallel increase in case fatality.

Historical change of suicide seasonality in the canton of zurich, Switzerland

Current research is yielding an increasingly heterogeneous picture of suicide seasonalities: They seem to depend on methods and, moreover, they seem to have smoothed in recent decades. This work examines the latter issue by comparing suicide seasonalities in the canton of Zurich, Switzerland, in the 16 th -18 th centuries, 1901-1920 and 1969-94. The results indicate shifts of peaks and lows on suicide seasonalities over the centuries, with a smoothing of seasonalities toward the 21 th century. The recent period does not show any suicide seasonality at all. The canton of Zurich seems to be ahead of the general trend found in other regions of Switzerland.

Suicides in the midnight sun--a study of seasonality in suicides in West Greenland

Greenland is the most extreme of human habitats in regard to annual changes in natural light. From being very low, the rate of suicides in Greenland has increased during the past few decades to be among the highest in the world. Several studies have shown seasonality in suicides with spring or summer peaks, but this has not been previously shown in Greenland. Official data from 1968 to 1995 from West Greenland were pooled. A significant seasonality in the 833 suicides was found using Rayleigh's test, a peak in June and a trough in the winter. Suicides increased during the period, and reached high rates in most age groups, up to 577 per 100,000 person-years in men aged 15-24 years in 1990, and up to 147 per 100,000 person-years in women aged 15-24 years in 1995. Violent methods of suicide were used by 93%. Depression has been reported uncommonly. High alcohol intake and extended periods of light in the summer may contribute to impulsive-aggressive summer suicides.

Seasonal fluctuation of suicide in Hungary between 1970-2000

The authors studied the seasonal fluctuation of suicide events in Hungary in a 31-year period. A summer maximum and a winter minimum were found in both genders. A second autumn peak did not occur among women. The suicide rate of Hungary fell markedly in 1998, parallel with the fundamental political-economical-social changes in the country. After 1988 the ANOVA statistic did show a moderate decrease in the seasonal fluctuation but only among those under 29 years of age. This young generation was the real "winner" of the deep social changes which suggests an indirect connection between the decrease of the seasonal fluctuation of suicide and the socio-political changes.

Sex-specific time patterns of suicidal acts on the German railway system. An analysis of 4003 cases

OBJECTIVE

To examine sex-specific time patterns of suicidal behaviour on railway tracks as basis of suicide preventive strategies.

METHOD

Cases were derived from the National Central Registry of all person accidents on the German railway net (STABAG) between 1997 and 2002 satisfying the operational definition of suicidal behaviour and included sex, age, date, clock time and outcome of the incidence.

RESULTS

Over the 6-year observation period, 4003 fatal and non-fatal suicidal incidences were documented. Male to female ratio was 2.70:1 (p<0.0001). The female subgroup was significantly older than the male subgroup (p<0.0001). The monthly distribution revealed a bimodal pattern (p=0.01), particularly in men younger than 65 years, with an excess risk in April and September. This circannual pattern attenuated in the second half of the observation period as shown by adjusted Poisson regression. Monday and Tuesday proved to be high risk days for both sexes. For males and females, a bimodal diurnal distribution pattern with a morning and an evening peak was observed. While both sexes followed the same pattern in the winter half year, in summer females showed a pronounced excess risk in the morning hours while for men the evening peak was substantially amplified (p<0.0001). Risk assessment revealed a marked broadening by approximately 6 h of the time window in the summer half year compared to the winter half year.

LIMITATIONS

About 30% of cases were excluded because of missing data on sex specification. However, cases with and without sex information did not differ significantly in the variables under investigation.

CONCLUSION

The analysis revealed marked seasonal, weekly and diurnal peaks of railway suicide intensity. Differences between men and women indicate sex-specific processes underlying their suicidal behaviour. The findings may increase alertness of railway and security personal for particular vulnerable time windows of excess risk for railway suicides.

A comparison of seasonal variation between suicide deaths and attempts in Hong Kong SAR

BACKGROUND

Seasonal variations in suicide deaths and attempted suicides have been reported for many countries. Recent research has suggested that seasonal patterns of suicide deaths have diminished considerably. The seasonality pattern between attempts and completed ones are not the same. This paper is the first one to examine seasonal variation between suicide deaths and attempts simultaneously.

METHOD

Census and Statistics Department and the Hospital Authority provided mortality and morbidity data on suicides for the period 1997-2001 in Hong Kong SAR, respectively. Seasonal patterns of suicide deaths and attempts were examined by a harmonic analysis and a non-parametric chi-square test.

RESULTS

A significant seasonal variation was detected in suicide attempts with a markedly bi-seasonal pattern was found amongst females with a peak in May and October; only a cyclic pattern was observed for males with a peak in summer. The female attempters who used non-violent suicide methods contributed to the second peak in October. On the other hand, there was no evidence of significant differences in the seasonal distribution among the suicide deaths for males and females. Only a mild pattern was found amongst females involving in violent suicide deaths, while others can be treated as a random event and no significantly pattern was observed in our study. Overall, a significant difference in seasonal variation existed between suicide deaths and attempts (p-value<0.01).

CONCLUSIONS

This study reinforces the findings that seasonal variation in suicide appears to be diminishing. Also, suicide attempters and completed suicides in Hong Kong seem to arise from two non-identical but overlapping groups in the community.

Estimation of reporting delay and suicide incidence in Hong Kong

This paper uses a semi-parametric method to examine the reporting delay distribution in suicides in Hong Kong reporting system. The data arise from a rightly truncated situation in which only suicide cases registered before a specific time are known to have occurred; otherwise they are not recorded in the known death files even if they have occurred. It is shown that the poisoning-related suicide deaths have a longer reporting delay than other suicide methods. By modelling the reporting delay function, a Horvitz-Thompson-type estimator is suggested to adjust for reporting delay and to provide a more timely estimate of the suicide incidences for monitoring the suicide problem in Hong Kong. Based on these analyses, we recommended a suitable cut-off date to collect suicide cases occurring in the previous year and reported before this date in Hong Kong.

Cyclic time patterns of death from suicide in northern Finland

BACKGROUND

Time patterns of suicide have been attributed not only to social and psychological factors but also to direct geophysical effects. Seasonal variations in day length and temperature seem likely to contribute to the timing of the suicide process.

METHODS

We analysed all suicides (n=1658) committed in a northern province of Finland during a period of 153 months. Daily data on the number of suicides, local weather conditions and geomagnetic storms were compiled and modelled with Poisson regression using the province population as the denominator, and with the means of harmonic series for seasonal variation. Time series analysis of monthly numbers of suicides was carried out using the seasonal-trend decomposition procedure based on loess.

RESULTS

Marked fluctuations in the number of suicides occurred during the study period (P=0.01). There was significant seasonal variation in death from suicide (P=0.01), but analysis of the meteorological data showed no evidence of effect on the risk of suicide.

LIMITATIONS

Assessment of mental disorder or alcohol consumption was missing, since only data derived from death certificate was available for each case.

CONCLUSIONS

The seasonal effect was significant, but remained modest compared to sex and age as risk factors for suicide. Preventive measures need to be tailored according to time of the year.

Seasonality in suicide: a study of farming suicides in England and Wales

Seasonality in suicide rates has long been reported. Spring peaks in suicide deaths have been positively correlated with the proportion of the workforce engaged in agriculture. Some studies have indicated that suicides using violent methods are more likely to show seasonality. Recent research has suggested that seasonal patterns have diminished. This study examined deaths in male farmers, an occupational group which might be expected to be more vulnerable to seasonal influences because of the nature of their work and the relatively high proportion of farmers using violent methods for suicide. Data on suicides between 1982 and 1999 by males in England and Wales aged 15 years and over were provided by the Office for National Statistics. Seasonal patterns of suicide in farmers and nonfarmers were examined by nonparametric tests and harmonic analysis. No significant seasonal variation was found for farmers. For nonfarmers, although a chi-square test showed significant variation in monthly distribution, this was not found when a harmonic analysis was applied. There was no significant difference in the variation of violent suicides throughout the year. This study reinforces recent findings that seasonal variation in suicide appears to be diminishing, even in an occupational group where this might be expected.

Increasing seasonality of suicide in Australia 1970-1999

Previous studies have found that rates of suicide have a distinct annual rhythm with a peak in spring. Two recent European studies, however, have found that the amplitude of this rhythm has decreased over time. The purpose of this study was to examine whether such effects are found in Australia. Australian Bureau of Statistics data on all suicides in Australia 1970-1999 were analysed by spectral analysis. We found that suicide, violent suicide and suicide by males are seasonal and that the seasonal amplitude has increased over time. Males who use violent methods determine the seasonal effect. These results support previous findings that suicide and particularly violent suicide have a characteristic seasonal rhythm. However, the progressive increase in the amplitude of this rhythm over time in Australia is in direct contrast to other European findings. We suggest that this may be related to differences in patterns of anti-depressant use and also the effect of migration on the number of seasonally vulnerable individuals in Australia.

Birth cohort effects in New South Wales suicide, 1865-1998

OBJECTIVE

To examine birth cohort effects in New South Wales (NSW) suicide data (1865-1998).

METHOD

Aggregate suicide data were examined after controlling for age and period using descriptive statistics and Poisson regression modelling. Three approaches were applied to address the non-identification of age, period and cohort in age-period-cohort (APC) models of suicide.

RESULTS

Apparent cohort effects in male and female suicide using a minimum constraints APC model of age, period and cohort were no longer present in female suicide when a surrogate period APC model was used, and were absent in both male and female suicide when identifiable cohort effects were isolated using a 'drift' adjusted approach to APC modelling.

CONCLUSION

Increases in youth suicide rates in NSW occurring since the 1960s cannot be attributed to cohort effects, such as family influences on development. The causes of youth suicide are thus effects operating contemporaneously.

Suicide and political regime in New South Wales and Australia during the 20th century

STUDY OBJECTIVE

Australia has had a two party parliamentary political system for most of the period since its Federation in 1901, dominated either by a social democratic (Labor) or a conservative ideological perspective. This paper investigates whether such political differences at Federal and State levels have influenced suicide rates in the state of New South Wales (NSW) for the period 1901-1998.

DESIGN

Federal government type, NSW State government type, and combinations of both Federal and NSW State government type were examined. Poisson regression models were stratified by sex and controlled for the effects of age, annual change in gross domestic product, sedative availability, drought, and both world wars.

RESULTS

When both Federal and NSW State governments were conservative the relative risk of suicide for NSW men was 1.17 (p<0.001) and for women 1.40 (p<0.001) compared with both governments being Labor (1.00). A statistically significant linear trend (p<0.001) in suicide risk was evident across the continuum of Federal/State government combinations, from both Labor (lowest), to mixed (intermediate), to both conservative (highest).

CONCLUSION

Significantly higher suicide risk was associated with conservative government tenures compared with social democratic incumbents. Results are discussed in terms of the differences underpinning conservative and social democratic government programme ideology, and their relevance to Durkheim's theories of suicide, social regulation, and integration.

Seasonal variation in specific methods of suicide: a national register study of 20,234 Finnish people

BACKGROUND

Previous studies have suggested differences in seasonal variation of violent and non-violent suicides, but seasonal distribution of the specific methods of suicide is less clear.

METHOD

We investigated the seasonal distribution of the specific suicide methods for both genders during a 16-year period. The seasonal effect was explored by monthly ratio statistics from the large population-based data including all suicides in Finland during years 1980-1995 (n=20,234).

RESULTS

Hanging peaked in spring among both genders. In summer, the significant peaks were occurred in suicides by drowning, jumping and gassing among males. The bimodality in female suicides with autumn peaks was explained by poisoning and drowning. Traffic suicides showed substantial winter-troughs for both genders.

CONCLUSIONS

The results suggested that specific violent and nonviolent methods of suicides grouped into their traditional clusters on the basis of their seasonality, except suicides by gassing and shooting. The seasonal distribution in specific suicide methods should take into account in suicide prevention at clinical work and also it should be considered while determining which methods of suicides are regarded as violent or non-violent methods in research.

Evidence for lack of change in seasonality of suicide from Timiş County, Romania

Evidence from politically and socially stable countries in Northern Europe and the Southern Hemisphere indicates a marked decrease in the seasonality of suicide over the past two decades. Generalizabiity of this trend to societies in transition has not yet been investigated. Data for suicide by hanging in Timiş County of Romania show both a nondecrease in seasonality of suicide for the current transitional period (1990-98), relative to the last decade of the Communist regime (1980-89) and shifts in location for suicide peak and trough months. Recent decreases in the seasonality of suicide might not generalize to societies in transition, and research would improve from focusing on the "natural laboratories" these societies represent.

Seasonal variation in suicides and in admissions to hospital for mania and depression

BACKGROUND

The influence of seasons on mood disorders is controversial.

OBJECTIVE

To examine monthly variations in admissions for mania and depressions including variations with sex and age and correlations with frequencies of suicides.

METHODS

All admissions for mania or depression (N=4341) in a population of 1,800,000 with 35,285 admissions in the years 1992-1996 were analysed. All 14,503 suicides in Norway the years 1969-1996 were also analysed.

RESULTS

Admissions for depression had a significant monthly variation for women (chi(2)=29.78, df=11, P<0.005) with the highest peak in November and for men (chi(2)=19.69, df=11, P<0.05) with the highest peak in April. Among women increasing age correlated negatively with the range of monthly observed/expected ratios (r(s)=-0.943, N=6, P<0.01) and with a of maximal monthly observed/expected ratio (r(s)=-0.943, N=6, P<0.01). Among men suicides correlated with admissions for depression (r=0.647, N=12, P<0.05) and mania (r=0.678, N=12, P<0.05).

LIMITATIONS

The time of admission to hospital are not identical to onset of affective episode. The study was done retrospectively. No sociocultural or physical environmental data were investigated.

CONCLUSION

A hypothesis of an influence of seasons on mood disorders is supported. Younger women seem to be especially vulnerable.

Seasonal variation and meteotropism in suicide: clinical relevance of findings and implications for research

Seasonal asymmetry in yearly suicide occurrence is a long-observed phenomenon in psychiatric, suicidological and sociological research, and the effects of seasonal factors on suicidal behaviour have been the focus of a number of earlier studies. Taking into account limitations of data and methods, these studies have in general favoured interpretations based on psychosocial factors. Recent studies have challenged the widely held notion that seasonal effects on suicide are not influenced by age, gender or the circumstances of the act. The suicides committed with violent methods have been shown to follow clearer seasonal patterns than suicides by less violent methods, and differences have been found between male and female cycles of occurrence. The seasonal occurrence of suicides has also been found to differ significantly between the young and the elderly. The use of inappropriate statistics or age- and gender-biased samples may have hidden a seasonal component in some previous studies on attempted suicide. The absence of seasonality in earlier studies on attempted suicide was interpreted as depending upon the minor relevance of psychiatric and biological factors in non-fatal self-harm. However, recent studies have reported clear seasonality in attempted suicide samples, with older people showing greater seasonal effect. Recent literature after 1985 on seasonal variation and weather or climate influence in attempted and completed suicide is reviewed. Suggestions for research and the development of more effective preventative strategies are offered.