Diversity and change in suicide seasonality over 125 years

ANALYSIS OF TIME, PLACE AND METHOD OF SUICIDE IN THE AREA OF BJELOVAR-BILOGORA COUNTY IN THE 1988-2017 PERIOD

The aim of the study was to analyze changes in the number of suicides associated with seasonal variables, calendar month, time of day versus variable location and method of suicide. Data were obtained from the Analytical Police Department of Bjelovar-Bilogora County for the 1988-2017 period. The process of Croatian application process into the European Union, accompanied by economic and social changes, was a significant socioeconomic event, which divided the analyzed period into two parts. Significant changes in the impact of the analyzed variables on the suicides committed in the two observed periods were tested with the χ2-test and Fisher exact test. Consistency of the results, as well as absence of the impact of significant changes would show less susceptibility of the covariate variable to the effect of socioeconomic factors. In the case of time of day and location of the suicides, there was no significant difference when comparing results between the 1988-2004 and 2005-2017 periods; however, a statistically significant difference was confirmed when considering the month of suicide (February) and season (winter, borderline result for autumn). Statistically, the most significant changes were found in the methods of suicide. The two observed periods differed in the mean suicide rate.

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.

Patterns of suicide deaths in Hungary between 1995 and 2017

Hungary has had one of the highest suicide mortality rates in the world for decades. Investigating seasonality of suicide deaths is essential as its findings could be key elements in the prevention. In our study we have analyzed the seasonal effect in suicide mortality in relation to possible risk factors in Hungary during 1995–2017.

Data on the numbers of suicide deaths were obtained from a published online database. Negative binomial regression was employed to investigate the effect of possible risk factors and seasonal and annual trends in suicide rates. The seasonal effect was further investigated, adding a significant risk factor from the “initial” negative binomial regression.

The suicide risk was significantly (p < 0.001) higher in men than in women (incidence rate ratio: 3.48), and it increased with age and decreased with education level. Marriage was a protective factor against suicide. Annual suicide mortality declined significantly (p < 0.001 for trend) from 36.7 (95% confidence interval: 35.5–37.9) to 16.5 (15.7–17.3) per 100,000 persons per year during the study period. Significant seasonality was found in suicide rates with a peak in late June. Similar peaks were observed at each level of each risk factor. There were differences in peaks by suicide method. The peak of non-violent suicides was in early June; suicides committed by violent methods peaked half a month later.

This study suggests that there was a significant seasonal effect on suicide deaths between 1995 and 2017, which remained significant even in the presence of each risk factor. To our knowledge, this has been the first study to investigate the seasonal pattern so extensively in Hungary. Our findings confirm that the environmental effects are involved in the etiology of suicide mortality.

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Significant seasonality was found in suicide rates with a peak in late June.

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Seasonal effect remained almost unchanged after adjusting sociodemographic factors.

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There were differences in seasonal peaks by suicide method.

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Environmental effects are involved in the etiology of suicide mortality.

Suicide time-series structural change analysis in Portugal (1913-2018): Impact of register bias on suicide trends

BACKGROUND

Suicide is a potentially preventable cause of death. Epidemiology might help to identify death determinants and to monitor prevention strategies. Few studies address secular trends in suicide deaths, and even fewer describe trend-changes in relation to data collection/registration bias. Moreover, suicide is admittedly underreported. It is crucial to validate results in the context of other external causes of death trends, such as unintentional and undetermined intent deaths. We aimed to explore trends in suicide and other external causes of death in Portugal from the inception of registries until 2018, considering breaks in series.

METHODS

We collected data from all available official primary sources. We calculated cause-specific age-standardized death rates (SDR) by sex for ages equal or higher than 15 years with reference to the European Standard Population. We considered suicide (S), undetermined intent deaths (UnD), accidents (Accs), and all causes of death (ttMty). A time-series structural analysis was executed.

RESULTS

Suicide and other external causes of death rates were consistently higher in males than females. A global decline of deaths by suicide, undetermined intention and unintentional is observable. Breakpoints in years 1930, 1954, 1982, 2000-2001 were associated with major changes in deaths registration procedures or methodology.

CONCLUSIONS

The epidemiology of suicide in Portugal has changed over 106 years. However, adjusted data and consideration of bias reduce trends fluctuation. Trend changes are akin to specific changes in methodology of death registry. Suicide surveillance will improve with more reliable and stable procedures.

Impacts of Social Distancing During the COVID-19 Outbreaks in Korea: Level 1 Trauma Center Data of Domestic Incidents and Intentional Injury

OBJECTIVES

As a protective measure to slow down the transmission of coronavirus disease 2019 in Korea, social distancing was implemented from February 29th, 2020. This study aimed to evaluate the prevalence of domestic incidents and intentional injury during March 2020 when social distancing was in effect.

METHODS

There were 12,638 patients who visited the Level 1 trauma center of Chungnam province with injuries from domestic incidents, familial discord, and intentional injury. The prevalence of injuries during March 2020 was compared with the average of the previous 5 years, and the average for every March between 2015 and 2019.

RESULTS

The prevalence of domestic incidents in March 2020 was significantly higher than the 5-year average, and the average for every March from 2015 to 2019 (p < 0.001). Familial discord (p = 0.002) and intentional injury (p = 0.031) were more frequently observed in March 2020. Adolescents showed a markedly higher level of intentional injury in March 2020 than in both the 5-year average (p = 0.031), and average for every March over the previous 5 years (p = 0.037).

CONCLUSION

The prevalence of domestic incidents and intentional injury were significantly higher during the period of social distancing in Korea. There is a need for social consensus, better policies, and psychological support services, especially if faced with a second or third wave of coronavirus disease.

Seasonality of suicide: a multi-country multi-community observational study

AIMS

We aimed to investigate the heterogeneity of seasonal suicide patterns among multiple geographically, demographically and socioeconomically diverse populations.

METHODS

Weekly time-series data of suicide counts for 354 communities in 12 countries during 1986-2016 were analysed. Two-stage analysis was performed. In the first stage, a generalised linear model, including cyclic splines, was used to estimate seasonal patterns of suicide for each community. In the second stage, the community-specific seasonal patterns were combined for each country using meta-regression. In addition, the community-specific seasonal patterns were regressed onto community-level socioeconomic, demographic and environmental indicators using meta-regression.

RESULTS

We observed seasonal patterns in suicide, with the counts peaking in spring and declining to a trough in winter in most of the countries. However, the shape of seasonal patterns varied among countries from bimodal to unimodal seasonality. The amplitude of seasonal patterns (i.e. the peak/trough relative risk) also varied from 1.47 (95% confidence interval [CI]: 1.33-1.62) to 1.05 (95% CI: 1.01-1.1) among 12 countries. The subgroup difference in the seasonal pattern also varied over countries. In some countries, larger amplitude was shown for females and for the elderly population (≥65 years of age) than for males and for younger people, respectively. The subperiod difference also varied; some countries showed increasing seasonality while others showed a decrease or little change. Finally, the amplitude was larger for communities with colder climates, higher proportions of elderly people and lower unemployment rates (p-values < 0.05).

CONCLUSIONS

Despite the common features of a spring peak and a winter trough, seasonal suicide patterns were largely heterogeneous in shape, amplitude, subgroup differences and temporal changes among different populations, as influenced by climate, demographic and socioeconomic conditions. Our findings may help elucidate the underlying mechanisms of seasonal suicide patterns and aid in improving the design of population-specific suicide prevention programmes based on these patterns.

Assessing Seasonality Variation with Harmonic Regression: Accommodations for Sharp Peaks

The use of the harmonic regression model is well accepted in the epidemiological and biostatistical communities as a standard procedure to examine seasonal patterns in disease occurrence. While these models may provide good fit to periodic patterns with relatively symmetric rises and falls, for some diseases the incidence fluctuates in a more complex manner. We propose a two-step harmonic regression approach to improve the model fit for data exhibiting sharp seasonal peaks. To capture such specific behavior, we first build a basic model and estimate the seasonal peak. At the second step, we apply an extended model using sine and cosine transform functions. These newly proposed functions mimic a quadratic term in the harmonic regression models and thus allow us to better fit the seasonal spikes. We illustrate the proposed method using actual and simulated data and recommend the new approach to assess seasonality in a broad spectrum of diseases manifesting sharp seasonal peaks.

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.

Where are weather-suicide associations valid? An examination of nine US counties with varying seasonality

There has been much research on the associations between weather variables and suicide rates. However, the state of understanding has remained rather stagnant due to many contradictory findings. The purpose of this project is to examine a larger database of suicides that includes a longer and more recent period of record (1975-2010) across numerous locations in the USA. In all, we examine nine total counties (and the primary city associated with them) with a special effort made to compare locations with varying degrees of temperature seasonality: Cook (Chicago), Fulton (Atlanta), King (Seattle), Los Angeles (Los Angeles), Maricopa (Phoenix), Miami-Dade (Miami), Philadelphia (Philadelphia), Salt Lake (Salt Lake City), and St. Louis (St. Louis). We first examine the unique seasonal cycle in suicides evident in each locale and then use distributed lag nonlinear modeling (DLNM) to relate the suicide data to daily surface temperatures. Results suggest that a late spring/summer peak generally exists in suicide rates, and above average temperatures are associated with increased suicide risk in almost all study counties. Further, it appears that these associations can be found in both mid-latitude and sub-tropical climate types.

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.

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.

Diminishing seasonality of self-harm: Temporal trends in Hong Kong SAR

BACKGROUND

The study of temporal variation in self-harm is important to understanding the underlying mechanisms of its occurrence. There are fewer studies on temporal variation in self-harm than in suicide. The aim of this study was to examine the seasonality of self-harm in Hong Kong and to test the hypothesis of diminishing seasonality.

METHODS

We used secondary data from medical records of self-harm obtained from all the public hospitals in Hong Kong under the management of the Hospital Authority. We identified 59,473 distinct episodes involving 36,411 patients. From these, monthly statistics of self-harm from January 2002 to December 2011 were calculated. Harmonic analysis was conducted to examine the presence and magnitude of seasonality.

RESULTS

A bi-seasonal pattern alongside a stronger one-cycle pattern from 2002 to 2006 was identified. During the period 1997-2001, this contracted to a one-cycle pattern with a peak in summer (May to July) and a nadir in winter (December). The magnitude of seasonality diminished greatly, as shown by harmonic analysis. The extent of diminishing seasonality was larger among women and people under 55 years old.

LIMITATIONS

The study covered only self-harm patients who had visited a hospital. Cases which required no medical attention and those where the patient consulted private doctors could not be included, indicating bias towards more severe cases of injury and poisoning.

CONCLUSION

This study provides some evidence of diminishing and even vanishing seasonality of self-harm in Hong Kong, a phenomenon mainly found in younger individuals. It could be related to the increasing use of social media to connect people, especially the younger generation. The impact of seasonal events and activities, as in the past, has become less significant in the social media era.

Seasonality of suicide behavior in Northwest Alaska: 1990-2009

OBJECTIVES

Suicide is a leading cause of death worldwide, and disproportionately affects Indigenous populations. Seasonal suicide patterns are variable in the literature, and could offer novel approaches to the timing and focus of prevention efforts if better understood. With a suicide surveillance system in place since 1989, this study offers an unprecedented opportunity to explore seasonal variations in both fatal and non-fatal suicide behavior in an Indigenous Arctic region.

STUDY DESIGN

Cross-sectional.

METHODS

In this descriptive study, we analyzed data collected from 1990 to 2009 in the rural northwest region of Alaska, both graphically and using the chi-squared test for multinomials.

RESULTS

We found a significant monthly variation for suicide attempts, with a peak in suicide behavior observed between April and August (P = 0.0002). Monthly variation was more pronounced among individuals ≤29 years of age, and was present in both males and females, although the seasonal pattern differed by sex.

CONCLUSIONS

Our findings of a significant seasonal pattern in suicide behavior, with monthly variation (summer peak) in non-fatal suicide behavior among younger age groups, and among both males and females can assist planners in targeting subpopulations for prevention at different times of the year.

Climate change but not unemployment explains the changing suicidality in Thessaloniki Greece (2000-2012)

INTRODUCTION

Recently there was a debate concerning the etiology behind attempts and completed suicides. The aim of the current study was to search for possible correlations between the rates of attempted and completed suicide and climate variables and regional unemployment per year in the county of Thessaloniki, Macedonia, northern Greece, for the years 2000-12.

MATERIAL AND METHODS

The regional rates of suicide and attempted suicide as well as regional unemployment were available from previous publications of the authors. The climate variables were calculated from the daily E-OBS gridded dataset which is based on observational data

RESULTS

Only the male suicide rates correlate significantly with high mean annual temperature but not with unemployment. The multiple linear regression analysis results suggest that temperature is the only variable that determines male suicides and explains 51% of their variance. Unemployment fails to contribute significantly to the model. There seems to be a seasonal distribution for attempts with mean rates being higher for the period from May to October and the rates clearly correlate with temperature. The highest mean rates were observed during May and August and the lowest during December and February. Multiple linear regression analysis suggests that temperature also determines the female attempts rate although the explained variable is significant but very low (3-5%)

CONCLUSION

Climate variables and specifically high temperature correlate both with suicide and attempted suicide rates but with a different way between males and females. The climate effect was stronger than the effect of unemployment.

Relationship of suicide rates with climate and economic variables in Europe during 2000-2012

BACKGROUND

It is well known that suicidal rates vary considerably among European countries and the reasons for this are unknown, although several theories have been proposed. The effect of economic variables has been extensively studied but not that of climate.

METHODS

Data from 29 European countries covering the years 2000-2012 and concerning male and female standardized suicidal rates (according to WHO), economic variables (according World Bank) and climate variables were gathered. The statistical analysis included cluster and principal component analysis and categorical regression.

RESULTS

The derived models explained 62.4 % of the variability of male suicidal rates. Economic variables alone explained 26.9 % and climate variables 37.6 %. For females, the respective figures were 41.7, 11.5 and 28.1 %. Male suicides correlated with high unemployment rate in the frame of high growth rate and high inflation and low GDP per capita, while female suicides correlated negatively with inflation. Both male and female suicides correlated with low temperature.

DISCUSSION

The current study reports that the climatic effect (cold climate) is stronger than the economic one, but both are present. It seems that in Europe suicidality follows the climate/temperature cline which interestingly is not from south to north but from south to north-east. This raises concerns that climate change could lead to an increase in suicide rates. The current study is essentially the first successful attempt to explain the differences across countries in Europe; however, it is an observational analysis based on aggregate data and thus there is a lack of control for confounders.

Seasonal Pattern in Suicide in Iran

Background:

Various studies have shown a seasonal pattern in suicide in the developed societies; however, this pattern is not taken into consideration in most countries including Iran.

Objectives:

The current paper studied the seasonal pattern of committing suicide in Northern Iran.

Materials and Methods:

The present study was a longitudinal study with time series features. Subject included suicide attempts recorded by emergency wards of all hospitals in Mazandaran province, Iran. The variable time, in this study, was defined as each month of study years (2005 - 2011), which included 84 monthly time points. To analyze data, the Student’s independent t-test and analysis of variance (ANOVA) test were used.

Results:

Of the 14,437 suicide attempts reported during the seven-year period, 5359 (37.1%) were related to males. Suicide attempts reached a peak in June (1418 cases) and November (1352 cases), but were at their lowest level in March (991 cases) (P = 0.877).

Conclusions:

The suicide seasonality range is broad in this part of Iran. Moreover, there were two noticeable suicide peaks in June and November.

Suicide around public holidays

OBJECTIVE

To examine the frequency of suicides on holidays and special days of the year, specifically in Queensland, Australia.

METHODS

We analysed data from the Queensland Suicide Register between 1990 and 2009. The days examined were: Easter, Christmas, New Year, Valentine's Day and Anzac Day. We compared suicide cases on these days with the average counts for periods before and after the days.

RESULTS

There was a statistically significant increase in suicides on Christmas Eve and on New Year's Day. Our results are discussed in light of trends reported in the literature.

CONCLUSION

The beginning and end of the festive season are times when special attention is warranted for those with a heightened risk of suicide.

Stable time patterns of railway suicides in Germany: comparative analysis of 7,187 cases across two observation periods (1995-1998; 2005-2008)

BACKGROUND

The majority of fatalities on the European Union (EU) railways are suicides, representing about 60% of all railway fatalities. The aim of this study was to compare time patterns of suicidal behaviour on railway tracks in Germany between two observation periods (1995-1998 and 2005-2008) in order to investigate their stability and value in railway suicide prevention.

METHODS

Cases were derived from the National Central Registry of person accidents on the German railway network (STABAG). The association of daytime, weekday and month with the mean number of suicides was analysed applying linear regression. Potential differences by observation period were assessed by adding observation period and the respective interaction terms into the linear regression. A 95% confidence interval for the mean number of suicides was computed using the t distribution.

RESULTS

A total of 7,187 railway suicides were recorded within both periods: 4,102 (57%) in the first period (1995-1998) and 3,085 (43%) in the second (2005-2008). The number of railway suicides was highest on Mondays and Tuesdays in the first period with an average of 3.2 and 3.5 events and of 2.6 events on both days in the second period. In both periods, railway suicides were more common between 6:00 am and noon, and between 6:00 pm and midnight. Seasonality was only prominent in the period 1995-1998.

CONCLUSIONS

Over the course of two observation periods, the weekday and circadian patterns of railway suicides remained stable. Therefore, these patterns should be an integral part of railway suicide preventive measures, e.g. gatekeeper training courses.

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

OBJECTIVES

Suicide mortality varies in both the short and long term. Our study examines suicide mortality in Finland and Sweden from the 1750s until today. The aim of our study is to detect any seasonal peaks in suicide rates and examine their temporal evolution to suggest a mechanism that may explain such peaks.

METHOD

We acquired the study material from the Finnish and Swedish cause of death statistics (257,341 deaths by suicide) and the relevant population gender structure data. We then separately calculated the annual male and female suicide rates per 100,000 inhabitants. We analysed the suicide peaks, calculating factors of proportionality for the available data by dividing the suicide rates in the peak months (May and October) by the annual suicide rates.

RESULTS

Suicide rates in Finland and Sweden peak twice a year. Both men and women in both countries most often commit suicide in May. There is another peak in October, with the exception of Finnish men. These suicide peaks coincide with a temperature increase in May and the biggest annual drop in temperature in October. We also observed a monotonic long-term change in the Swedish statistics, but not in the Finnish data. Our hypothesis is that seasonal variation in suicide rates may be caused by abrupt temperature changes twice a year that trigger the activity in brown adipose tissue and deepen depression.

CONCLUSION

While the overall suicide mortality rates varied considerably, the monthly proportions in May did not. This finding suggests a routine factor underlying the spring peak in suicide mortality.

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.

Suicide deaths and nonfatal hospital admissions for deliberate self-harm in the United States. Temporality by day of week and month of year

BACKGROUND

No one knows whether the temporality of nonfatal deliberate self-harm in the United States mirrors the temporality of suicide deaths.

AIMS

To analyze day- and month-specific variation in population rates for suicide fatalities and, separately, for hospital admissions for nonfatal deliberate self-harm.

METHODS

For 12 states, we extracted vital statistics data on all suicides (n = 11,429) and hospital discharge data on all nonfatal deliberate self-harm admissions (n = 60,870) occurring in 1997. We used multinomial logistic regression to analyze the significance of day-to-day and month-to-month variations in the occurrence of suicides and nonfatal deliberate self-harm admissions.

RESULTS

Both fatal and nonfatal events had a 6%-10% excess occurrence on Monday and Tuesday and were 5%-13% less likely to occur on Saturdays (p < .05). Males were more likely than females to act on Wednesdays and Saturdays. Nonfatal admission rates were 6% above the average in April and May (p < .05). In contrast, suicide rates were 6% above the average in February and March and 8% below it in November (p < .05).

CONCLUSIONS

Suicides and nonfatal hospital admissions for deliberate self-harm have peaks and troughs on the same days in the United States. In contrast, the monthly patterns for these fatal and nonfatal events are not congruent.

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.

Re-examination of the seasonality of suicide in Taiwan during 1991-2008: a population-based study

The purpose of the present study was to re-examine the monthly distribution of suicide death rates and the change of the suicide seasonality in Taiwan during 1991-2008. The monthly suicide death rates of the total, male and female populations during January 1991-December 2008 were obtained from a population-based database. There was an upward trend. The means of the monthly suicide rates after adjusting the calendar effect and the upward trend were compared. The suicide data were further analysed in three 6-year periods to explore the change of seasonality. During 1991-2008 in Taiwan, suicide rates had significant peaks in April and May, and nadirs in January and December. The monthly distributions varied during 1991-1996, 1997-2002 and 2003-2008 in the patterns and the statistical significance. There was no linear trend for the change of the seasonality of suicide death rate.

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.

The hypothalamic-pituitary-adrenal axis and serotonin abnormalities: a selective overview for the implications of suicide prevention

Suicidal behavior and mood disorders are one of the world's largest public health problems. The biological vulnerability for these problems includes genetic factors involved in the regulation of the serotonergic system and stress system. The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates the body's response to stress and has complex interactions with brain serotonergic, noradrenergic and dopaminergic systems. Corticotropin-releasing hormone and vasopressin act synergistically to stimulate the secretion of ACTH that stimulates the biosynthesis of corticosteroids such as cortisol from cholesterol. Cortisol is a major stress hormone and has effects on many tissues, including on mineralocorticoid receptors and glucocorticoid receptors in the brain. Glucocorticoids produce behavioral changes, and one important target of glucocorticoids is the hypothalamus, which is a major controlling center of the HPA axis. Stress plays a major role in the various pathophysiological processes associated with mood disorders and suicidal behavior. Serotonergic dysfunction is a well-established substrate for mood disorders and suicidal behavior. Corticosteroids may play an important role in the relationship between stress, mood changes and perhaps suicidal behavior by interacting with 5-HT1A receptors. Abnormalities in the HPA axis in response to increased levels of stress are found to be associated with a dysregulation in the serotonergic system, both in subjects with mood disorders and those who engage in suicidal behavior. HPA over-activity may be a good predictor of mood disorders and perhaps suicidal behavior via abnormalities in the serotonergic system.

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.

Gender differences in antidepressant use-related seasonality change in suicide mortality in Hungary, 1998-2006

OBJECTIVES

Studies show that the seasonality of suicide (spring/early summer peak, winter low) is mainly the consequence of the seasonal incidence of depression-related suicides. The aim of the present study was to analyse the relationship between increasing antidepressant utilization and national suicide rate of Hungary between 1998 and 2006, with particular regard to seasonal patterns and gender differences.

METHODS

Time trend analysis (ARIMA) had been applied to investigate the correlation between the trend of antidepressant prescription and both of suicide rates and seasonality index.

RESULTS

During the 9 years of the study period there was a significant (P<0.001) correlation between the steadily increasing antidepressant prescription (113%) and continuous decline in total national suicide rate (23%) as well as both in females and males (21 and 23%, respectively), but this relationship was 8-fold stronger in males. Increasing antidepressant utilization was associated with significantly decreased seasonality of suicides only among males.

CONCLUSIONS

The results suggest that decreasing seasonality of suicides could be a good marker of lowering rate of depression-related suicides in the population particularly among males.

Suicidality and montelukast

BACKGROUND

Suicide is a serious public health problem. Prevention of suicide depends to a great degree on identification and mitigation of its risk factors. Allergy has been associated with mood and anxiety disorders, risk factors for suicidality. Antiallergic medication could modulate or mediate these predictive associations. Recently, the FDA issued a warning raising concerns about the suicidality potential of montelukast and other leukotriene (LT) antagonists.

OBJECTIVE

The purpose of this review is to integrate the emerging interpretations of the link between suicidality, suicide risk factors, allergy and treatment of allergy in particular, with LT antagonists.

METHODS

We reviewed the available reports on the possible relationships between montelukast, allergy, suicide, suicidality and suicide risk factors. We also present the positions of the FDA, manufacturer, and national organizations of allergists and immunologists on the possible role of montelukast in suicidality.

CONCLUSION

At present, there is insufficient data to prove that there is a link between montelukast and suicidality. Inquiring about mood changes and suicidal ideation should be integrated in general medical practice.

Relationship among latitude, climate, season and self-reported mood in bipolar disorder

OBJECTIVE

Many researchers have analyzed seasonal variation in hospital admissions for bipolar disorder with inconsistent results. We investigated if a seasonal pattern was present in daily self-reported daily mood ratings from patients living in five climate zones in the northern and southern hemispheres. We also investigated the influence of latitude and seasonal climate variables on mood.

METHOD

360 patients who were receiving treatment as usual recorded mood daily (59,422 total days of data). Both the percentage of days depressed and hypomanic/manic, and the episodes of depression and mania were determined. The observations were provided by patients from different geographic locations in North and South America, Europe and Australia. These data were analyzed for seasonality by climate zone using both a sinusoidal regression and the Gini index. Additionally, the influence of latitude and climate variables on mood was estimated using generalized linear models for each season and month.

RESULTS

No seasonality was found in any climate zone by either method. In spite of vastly different weather, neither latitude nor climate variables were associated with mood by season or month.

CONCLUSION

Daily self-reported mood ratings of most patients with bipolar disorder did not show a seasonal pattern. Neither climate nor latitude has a primary influence on the daily mood changes of most patients receiving medication for bipolar disorder.

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.

Seasonality of suicide in the city of Sao Paulo, Brazil, 1979-2003

OBJECTIVE: To evaluate suicide seasonality in the city of São Paulo within an urban area and tropical zone. METHOD: Suicides were evaluated using the chi-square test and analysis of variance (ANOVA) by comparing monthly, quarterly and half-yearly variations, differentiating by gender. Analyses of time series were carried out using the autocorrelation function and periodogram, while the significance level for seasonality was confirmed with the Fisher's test. RESULTS: The suicides of the period between 1979 and 2003 numbered 11,434 cases. Differences were observed in suicides occurring in Spring and Autumn for the total sample (ANOVA: p-value = 0.01), and in the male sample (ANOVA: p-value = 0.02). For the analysis of time series, seasonality was significant only for the period of 7 months in the male sample (p-value = 0.04). DISCUSSION: In this study, no significant seasonal differences were observed in the occurrences of suicides, with the exception of the male sample. The differences observed did not correspond with the pattern described in studies carried out in temperate zones. Some of the climatic particularities of the tropical zone might explain the atypical pattern of seasonality of suicides found in large populations within an urban area and tropical zone.

Accentuation of suicides but not homicides with rising latitudes of Greenland in the sunny months

BACKGROUND

Seasonal variation in suicides has been shown in many countries. We assessed the seasonality and the variation with latitude in suicides and homicides, and the impact of alcohol on the seasonality in suicides.

METHODS

Official computerized registers on causes of death in all Greenland during 1968-2002 were used. Sales data on beer from one of the major food store chains for July 2005-June 2006 were examined. Seasonal variation was assessed by Rayleigh's test for circular distributions.

RESULTS

There were a total of 1351 suicides and 308 homicides. The suicides rate varied from 4.2/100 000 person-years in 1971 to 128.4/100 000 person-years in 1987. The homicide rate varied from 2.1/100000 person-years in 1969-1970 to 34.8/100 000 person-years in 1988. Out of the 1351 suicides, 80.5% were committed by men and 19.5% by women. Median age was 25 years (n = 1351; Range 11-84 years). Violent methods of suicide were used in 95% of all cases (n = 1286). Out of the 308 homicide victims, 61% were men and 39% were women, and 13% were killed in multiple homicide events.There was a significant seasonal variation with peaks in June and troughs in the winter in all suicide cases (n = 1351, r = 0.07; Z = 7.58, p < 0.001), in violent suicides (n = 1286; r = 0.07; Z = 6.97; p < 0,001), in suicides in men (n = 1087; r = 0.07; Z = 5.39; p < 0.002) , and in women (n = 264; r = 0.10; Z = 2.36; p < 0.05), but not in homicides nor in consumption of beer. There was a bi-phasic seasonal variation in suicide victims where an alcohol-related condition was included in the death certificate. Suicides were more concentrated in the summer months north of the Arctic Circle (n = 577, r = 0.09, Z = 4.45, p < 0.01) than south of it (n = 769, r = 0.07, Z = 3.76, p < 0.002) and most concentrated in North Greenland (n = 33; r = 0.35; Z = 4.11; p < 0.01), where 48% of suicides occurred during the period of constant light. When including astronomical twilight in the constant light period 82% occurred during this time.

CONCLUSION

There was a concentration of suicides but not homicides in the summer months in all Greenland. The concentration was most pronounced at high latitudes.

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

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.

Changes in the seasonality of suicides over time in Slovenia, 1971 to 2002. Amplitude is only positively related to suicide rates among females

BACKGROUND

Changes in the suicide rate within one region over time had been hypothesised to correspond to changes in suicide seasonality: a recent investigation from Italy confirmed such an assumption. Data from Slovenia were investigated to further evaluate the links between suicide rates and seasonal amplitude.

METHODS

A total of 14325 male suicides and 4350 female suicides occurring in Slovenia from 1971 to 2002 were investigated with harmonic spectral analysis to extract their monthly seasonal dispersion by eight-year intervals. Changes in rate over time were analysed with a test for trend based on regression analysis.

RESULTS

The suicide rates of both males and females increased over time, with an evident peak in the 1987-1994 period and a decrease thereafter. Seasonality decreased across time in both sexes; however, no change of the peak was observed over time. The amplitude of the major 12-month cycle was slightly positively related to suicide rates, but the correlation was only statistically significant among females (P=0.0053; males: P=0.22).

LIMITATIONS

Data could not be analysed according to age, the method of suicide, or the diagnosis attributable to the deceased, since this information was not available.

CONCLUSION

The study confirmed that the seasonal effect on mortality by suicide is positively related to suicide rates, so much so that changes in suicide rates over time correspond to changes in suicide seasonality, but in Slovenia this effect was only evident among females, further pointing towards differences by sex in the mechanics leading to suicide.

Facts and myths about seasonal variation in suicide

The prevalence of suicide presents a universal seasonal pattern. In the Northern hemisphere, suicides peak during spring and early summer and the trough occurs during winter. This peculiar pattern might be counterintuitive for everyday reasoning. Data from 1,093 medical and psychology undergraduates from Austria (382 men and 711 women; M age 25.0 yr., SD=6.6) indicated an almost perfectly reversed pattern of beliefs about suicide seasonality compared with the actual seasonal distribution. The vast majority of respondents believed the peak to be located in late autumn and early winter and the trough occurring in late spring and the summer months. Implications for education and practice are discussed.

Global warming possibly linked to an enhanced risk of suicide: data from Italy, 1974-2003

BACKGROUND

The global increase in surface temperature (known as global warming) was found to impact on mortality through ill health, particularly among the elderly and in summer. This study sets out to explore the impact of global warming on suicide mortality, using data from Italy.

METHODS

Monthly data on suicide mortality and temperature were obtained for a 30-year period (from January 1974 to December 2003), and the relation between them was investigated using the Gaussian low-pass filter, linear correlation analysis and rank analysis.

RESULTS

For males, increasing anomalies in monthly average temperatures associated to a higher monthly suicide mean from May to August and, to a lower extent, in November and December. In January, on the other hand, increasing anomalies in monthly average temperatures appeared to be coupled to a lower number of suicides. For females, the links between temperature and suicides are less consistent than for males, and sometimes have a reverse sign, too.

LIMITATIONS

Data could not be analyzed according to age, since this information was not available across the whole time interval. The use of monthly data, instead of daily data (unavailable), is another major limitation of this study.

CONCLUSIONS

An improvement in the ability of communities to adjust to temperature changes by implementing public health interventions may play an important part in preserving the wellness of the general population, and also in limiting the worst consequences of suicidal behaviour.

Relationship between daily suicide counts and temperature in England and Wales

BACKGROUND

Seasonal fluctuation in suicide has been observed in many populations. High temperature may contribute to this, but the effect of short-term fluctuations in temperature on suicide rates has not been studied.

AIMS

To assess the relationship between daily temperature and daily suicide counts in England and Wales between 1 January 1993 and 31 December 2003 and to establish whether heatwaves are associated with increased mortality from suicide.

METHOD

Time-series regression analysis was used to explore and quantify the relationship between daily suicide counts and daily temperature. The impact of two heatwaves on suicide was estimated.

RESULTS

No spring or summer peak in suicide was found. Above 18 degrees C, each 1 degrees C increase in mean temperature was associated with a 3.8 and 5.0% rise in suicide and violent suicide respectively. Suicide increased by 46.9% during the 1995 heatwave, whereas no change was seen during the 2003 heat wave.

CONCLUSIONS

There is increased risk of suicide during hot weather.

Seasonality and suicide in Italy: amplitude is positively related to suicide rates

BACKGROUND

Recent studies have reported changes in the time patterns of suicide, with conflicting findings regarding the direction of these changes: data from Italy were investigated to evaluate the influence of recent social and medicine-related changes on the seasonality of suicides in the country.

METHODS

A total of 71,227 male suicides and 26,466 female suicides occurring in Italy from 1974 to 2003 were investigated with harmonic spectral analysis to extract their monthly seasonal dispersion by five-year intervals.

RESULTS

The suicide rates of both males and females showed a rising trend, with an evident peak in the 1987-1994 period and a decrease thereafter. Seasonality of suicides, with a clear peak in spring as against the other seasons, accounted for a statistically significant proportion of total variance: around 40% among males and 39% among females. Seasonality did not change across time in a relevant way; however, an anticipation of the peak was observed in both males and females over time, with amplitude increasing or decreasing as a function of yearly suicide rates.

LIMITATIONS

Data could not be analysed according to age or to the method of suicide, since this information was not available across the whole time interval.

CONCLUSION

The seasonal effect on mortality by suicide is positively related to suicide rates, so much that changes in suicide rates over time correspond to changes in suicide seasonality.

Changes in the seasonality of suicides over time in Slovenia, 1971 to 2002

BACKGROUND

Recent studies have reported changes in the time patterns of suicide, with reduced seasonality in some European and Asian countries. Anyway conflicting data were reported on the fading of suicide seasonality, and in some countries a rising trend was reported.

METHODS

Harmonic spectral analysis was used to analyze all suicides in Slovenia in the years 1971 to 2002 (14,325 among males; 4350 among females). Analyses of overall changes are based on data aggregated by intervals of 8 years.

RESULTS

In both sexes, seasonal variance accounts for a statistically significant proportion of total variance (36.0% among males; 13.3% among females). Anyway in both sexes the season-attributable variance in the latest interval is considerably lower than in the preceding periods.

LIMITATIONS

Data could not be analyzed according to age or to mental disorder diagnosis, since this information was not available.

CONCLUSION

The seasonal effect on mortality by suicide is sensitive to change, but its causes seem not to be sex-dependant.