Background
The success of any suicide-prevention programme depends on our ability to identify and influence the factors that considerably increase the risk of suicide in the population. This risk is primarily affected by social psychological factors whose effects become particularly conspicuous in relation to certain social events. Several sociological and psychological models have been used to examine the theoretical background in studies investigating the impact of a wide range of social events on suicidal behaviour [
1‐
4]. However, these studies have predominantly investigated national events [
5‐
7].
It is well known that the average risk of suicide-related behaviour in certain sub-populations (age-related, professional, gender-related, or religious) may vary substantially [
8,
9]. Each subpopulation contributes to the general rate of suicide-related behaviour, however, not every sub-population is available for direct evaluation. Some of them are impermanent and changeable (concert audiences or football spectators), and others cannot be easily subjected to investigation (closed professional or religious communities). In such situations, it is necessary to obtain data using other approaches. We hypothesize that, just like national social events that affect the suicide-related behaviour of the entire population, local events confined to sub-populations may also affect the general rate of suicide-related behaviour in local populations. The variation of the latter would theoretically depend on how a mass gathering’s particular milieu affected the risk of suicide-related behaviour in the sub-population of its participants. If so, an analysis of the general population’s suicide-related behaviour rates with respect to mass gatherings might be useful as an indirect evaluation of the level of suicide-related behaviour in a sub-population of people participating in gatherings of various kinds, such as concerts, sports competitions, and religious events.
Music shows and concerts
To our knowledge, no research has been conducted on the effect of music shows on suicide, and existing studies have only a distant relation to this particular problem. Some lifetime studies have reported that attending certain kinds of cultural events may have a beneficial effect on physical health, social functioning, and vitality [
10]. However, one paper describes ‘epidemical mass fainting’ among those attending rock concerts [
11].
Sports events
Sports events appear to be the only kind of mass gatherings whose effects on suicide have been a subject to an epidemiological evaluation [
7]. Two earlier studies [
12,
13] found no significant changes in national suicide rates related to sports events. However, a Canadian study reported mixed results: whereas the general suicide rate was not affected by sports events, young males (15–34 years old) had an increased suicide risk during the hockey playoffs [
14]. A later analysis of the effects of professional sports games on suicide in major US cities reported a relationship between the games and suicide rates [
15].
As for the effect of a local team’s performance on suicide, a British study reported a significant short-term (12-hour) increase in deliberate self-poisonings after the defeat of a local football team [
16]. Another US study found that there were fewer suicides when the US Olympic ice hockey team beat the Soviet Union and on Super Bowl Sundays [
17].
All these investigations, however, examined mostly national and international sports events that affected a great part of the population. Moreover, these research findings give no clue as to whether attending a major sports event has an influence on suicide-related behaviour.
Mass religious events
A number of investigations show that religious festivities (e.g., Christmas) are followed by an increase in the suicide rate [
6]. However, practically no research has been conducted on whether mass gatherings carried out by religious organisations influence suicide-related behaviour rates.
At the same time, it is commonly accepted that religiosity is a factor that may decrease the risk of suicide-related behaviour. Durkheim perceived religious affiliation as a proxy for integration and regulation, which in his opinion affected the suicide rate [
1]. However, some authors suggest that the correlation between suicide and religious affiliation has disappeared [
18]. At the same time, the results of more recent representative cross-national investigations have demonstrated that in countries where religion retains a real social significance, the suicide level is the lowest. However, it must be noted that this phenomenon is typical only in countries that profess traditional religions [
19]. Conversely, it is well known that all mass suicides in recent decades were arranged exclusively by members of so-called new religious movements [
20].
Although the volume of psychiatric studies on the phenomenon of new religious movements is extremely limited, some studies have, nevertheless, evaluated the level of suicide-related behaviour among former and current devotees of new religious movements.
A study of 68 active devotees of Transcendental Meditation reported that 20% of them expressed serious suicidal tendencies [
21]. According to another study, 18.8% of 154 former new religious movement members had suicidal or self-destructive tendencies [
22]. Furthermore, a study of 400 former members of new religious movements found that, among other symptoms, 21% of them reported suicidal or self-destructive tendencies [
23]. Another study that evaluated 43 former members of the Word of Life new religious movement found that 63% of the group’s members ‘had experienced suicidal thoughts’ and 23% ‘had made a serious suicide attempt’ [
24]. It is rather significant that many studies have obtained similar results with regard to the suicide-related behaviour among current and former members of new religious movements.
It follows from the above that certain mass gatherings may influence the suicide rate in the population. The aim of this study is to provide a statistical evaluation of the possible relationship between mass gatherings in some relatively small urban sub-populations and the suicide rates of a major city.
Methods
Sample
The data used in this study are from the daily registrations of suicide-related incidents in the industrial city of Dnipropetrovsk, Central Ukraine (approximately 1 million residents) over a period of 6 years, 2005–2010. Data on suicide attempts (Type II, by self-poisoning) were obtained from the Dnipropetrovsk City Centre for Acute Poisoning. The total of 1,078 suicide attempt cases (Х60-Х69 according to the Tenth Revision of the International Classification of Diseases [ICD-10]) included 314 men and 764 women. Data on suicides were obtained from the Dnipropetrovsk Forensic Medical Examination Bureau. There were 1,027 suicides (Х60-Х75, X78, X80, X81, Х83), of which 802 were men and 225 were women. The main methods of suicide were as follows: hanging – 81.8%; jumping off a high place – 9.4%; firearm – 3.6%; sharp object – 3.4%; self-poisoning – 0.7%.
The obtained primary data were arranged as a daily time series. Daily sums of suicide-related behaviour acts for each sex and the total were calculated on the basis of primary data.
All the data used for this study were released with the official approval of the Department of Internal Affairs of the Dnepropetrovsk City Government. The data were impersonalized and non-identifiable.
Data on mass events
Data on the 427 mass events in Dnipropetrovsk for the years 2005–2010 are shown in Table
1. These events included 88 large concerts and 217 home and guest games of the local football team, Dnipro (playing in the national Premier League; see
http://www.fcdnipro.ua/). In addition, our study included 32 games of the national football team in qualifying games for the 2006 World Cup, EURO 2008, and the 2010 World Cup, as well as four games in the 2006 World Cup championship (see
http://www.fanatukr.com/). In all cases, we took into account the game results and official data on the number of local citizens who visited the Dnipro games in Dnipropetrovsk, as well as its games elsewhere.
Table 1
Mass events that were pertinent to different sub-populations in Dnipropetrovsk city from 2005 to 2010
Matches of local football team: |
At home | 105 | 1.20 |
Win | 53 | 1.00 |
Draw | 28 | 1.30 |
Defeat | 24 | 1.60 |
Away | 112 | 0.04 |
Win | 45 | 0.03 |
Draw | 36 | 0.04 |
Defeat | 31 | 0.05 |
Matches of national football team: |
Elimination games | 32 | n/i |
Win | 15 | n/i |
Draw | 8 | n/i |
Defeat | 9 | n/i |
Championship | 4 | n/i |
Win | 3 | n/i |
Defeat | 1 | n/i |
Large concerts | 88 | 0.60 |
Orthodox Church | 8 | n/i |
New religious movements | 78 | 0.30 |
With respect to religion, because the activities of religious organizations typically operate on a weekly basis, we took into account only non-regular, extraordinary gatherings. The Orthodox Church held eight such events to venerate miracle-working relics, which devotees associate with miraculous healing. New religious movements arranged 78 public mass events.
For gatherings where the average number of participants could be determined, it was possible to calculate their proportion with respect to the population of the city. Except for the football matches, no events were broadcast on TV.
Bivariate analysis
Data on suicide-related behaviour incidents are count variables conforming to the Poisson distribution with the share of zero counts ranging from 40.5 to 90.0%. We attempted to normalize the distribution by substituting the weekly total for the daily data. However, the Kolmogorov-Smirnov test showed that the data are still not normal and therefore non-parametric procedures are appropriate for the analysis.
The statistical evaluation of how a certain event influences the suicide-related behaviour risk poses a methodological problem. Because there is a considerable weekly pattern in the number of suicides [
25], one approach that we attempted involves comparing the risks in the 7 days following the event with those in the 7 days preceding the event. For each comparison the
relative risk (RR) was calculated as the ratio of the number of suicide-related behaviour incidents in a given period to the number of the same incidents in the control period. This is really an odds ratio whose significance can be estimated from a Poisson regression, where the dependent variable was the vector of counts after and before the event. The only independent variable is a two-level factor indicating which group the values came from [
26].
Although the comparison of suicide-related behaviour rates before and after events provides a means to establish the association between suicide behaviour and the events, the anticipation of some events may also influence suicide rates [
5,
6]. Therefore, we also used another approach, which consisted of comparing the average 7-day risks before and after each type of gathering to the average risks during all other days in the temporal sequence. The Mann–Whitney test and the Wilcoxon signed-ranks test for independent samples were used to make the comparisons.
The bivariate analyses and data manipulations were conducted using Microsoft Office Excel 2003 (Microsoft Corp. Redmond, WA, USA), PASW IBM Statistics version 18.0 (IBM, Armonk, NY, USA) and R language (R Foundation for Statistical Computing, Vienna, Austria).
Multivariate analysis
When bivariate analysis leads to rejection of the null hypothesis, this finding requires an estimation of the potential confounding effects of numerous socio-environmental variables. We, therefore, used the negative binomial regression, which is an appropriate procedure for count data with a large proportion of zero counts.
Dummy variables of events
The data on all types of mass gatherings and other events were represented as dummy variables: the 7 days of the estimated period were coded as ‘1’ and other days as ‘0’. For each type of regular or pre-announced event, two dummy variables were created: ‘days before the event’ and ‘days after the event’. Football games are represented by four dummy variables: ‘days before the event’, and three more after-the-event variables that coded separately for victories, drawn games, and defeats.
Covariates
A literature search of the MEDLINE database suggests there is an extensive set of the time-varying factors that may significantly influence suicide-related behaviour. We identified as many of these variables as possible and matched them with our suicide data. An additional file shows these variables and references in more details (see Additional file
1).
However, we did some additional analysis to select those independent variables that might be useful in a multivariate setting. We used Kendall’s tau-b correlation for continuous independent variables and selected only those that had significant correlations with any of the response variables.
With respect to dummy variables, we compared the response variables for the days designated as ‘1’ with those designated as ‘0’ in the procedures of the Mann–Whitney test and the Poisson regression described above. Those variables that yielded a significant result were selected for further model building.
After eliminating some collinear variables, we identified the following independent variables as covariates for model building:
Solar and planetary variables: daily number of sun spots, daily flux of protons >100 Mev, and the average daily Dst geomagnetic index;
Weather-climatic and seasonal variables: minimal daily temperature, change of minimal daily temperature compared with the previous day, daily sunshine time, and ‘month’ as a set of dummy variables (April being the base category);
Socio-economic variables: monthly birth rate in the city, monthly death rate, monthly rate of divorces, monthly inflation index, wage arrears per capita, monthly rate of unemployment, monthly rate of in-migration, monthly rate of international migration, national lottery jackpot in USD, and ‘day of week’ as a set of dummy variables (Friday being the base category);
Mental morbidity: daily urgent hospitalisation for mental treatment (except the cases of suicidal behaviour);
National events: state Orthodox feasts, and general elections.
Regression modelling
Although we did engage in exploratory analysis of each variable, we produced our models through a data-mining procedure in the R environment [
27]. As a first step in that process, we ran a stepwise Poisson regression of a dependent variable against all other independent variables. We ran the step procedure in both directions to account for the multicollinearity of relationships. To ensure the principle of minimal description length, we used Schwartz’s version of the Bayesian information criterion [
28]. In the next stage of our analysis, we ran a negative binomial regression to model the overdispersion parameter [
29], which turned out to be more adequate than the corresponding standard Poisson models.
Finally, to take into account the fact that we were running regressions on time-series data, we computed robust estimates using the ’sandwich’ approach [
30]. The last two stages of the analysis were done in the ‘Zelig’ interface using the ‘negbin’ function [
31].
Results
Bivariate analysis
Table
2 shows the significant findings obtained when comparing the data on suicide-related behaviour during the 7 days before and after various mass gatherings. Female suicide-related behaviour increased after a football game in the city (RR = 1.17;
p = 0.045). Male suicide attempts became more likely after a victory in an elimination game (RR = 3.50;
p = 0.027). Female suicide attempts (RR = 1.29;
p = 0.012), male suicides (RR = 1.24;
p = 0.027), and all secondary indices increased after mass events organized by new religious movements.
Table 2
Significant relative risks (RR) as ratio of suicidal incidents after and before some mass events
Suicide attempt |
Male | 1.14 (0.341) |
3.50
(0.027)
| 1.06 (0.699) |
Female | 1.12 (0.192) | 0.90 (0.686) |
1.29
(0.012)
|
Suicides |
Male | 0.96 (0.613) | 0.87 (0.518) |
1.24
(0.027)
|
Female | 1.36 (0.068) | 0.46 (0.117) | 0.92 (0.635) |
Suicide-related behaviour |
Male | 1.01 (0.943) | 1.08 (0.695) |
1.19 (0.037)
|
Female |
1.17 (0.045)
| 0.76 (0.246) |
1.19
(0.044)
|
Total | 1.08 (0.156) | 0.93 (0.653) |
1.19
(0.004)
|
Table
3 shows the significant findings when comparing the suicide-related behaviour risk in the urban population around the period of mass gatherings with that on all other days. We found a significant decrease in female suicide-related behaviour after large concerts (RR = 0.81;
p = 0.01), as well as a decrease in female suicide-related behaviour and suicide attempt after exhibitions of miracle-working relics (RR = 0.48;
p = 0.028 and RR = 0.46;
p = 0.041 respectively).
Table 3
Significant relative risk (RR) of suicide-related behaviour around the time of some mass events
Suicide attempt |
Male | 1.07 (0.531) | 1.36 (0.158) | 2.07 (0.317) | 1.00 (0.832) | 1.14 (0.185) |
Female | 0.83 (0.055) | 1.03 (0.826) | 0.60 (0.281) |
0.46
(0.041)
|
1.27
(0.004)
|
Suicides |
Male | 1.08 (0.333) | 1.31 (0.093) | 0.78 (0.572) | 1.00 (0.686) |
1.29
(0.006)
|
Female | 0.73 (0.071) | 1.00 (0.807) |
3.60
(0.001)
| 0.60 (0.381) | 1.00 (0.970) |
Suicide-Related Behaviour |
Male | 1.08 (0.141) |
1.32
(0.047)
| 1.12 (0.921) | 1.00 (0.895) |
1.25
(0.019)
|
Female |
0.81
(0.010)
| 1.02 (0.858) | 1.27 (0.843) |
0.48
(0.028)
|
1.21
(0.011)
|
Total | 0.95 (0.681) | 1.18 (0.316) | 1.19 (0.486) | 0.75 (0.119) |
1.23
(0.000)
|
A significant increase was evident for male suicide-related behaviour after the home defeat of the local football team (RR = 1.32; p = 0.047) and for female suicides before the national team played a World Cup game (RR = 3.60; p = 0.001). After mass events organized by new religious movements, there was a significant increase in female suicide attempts (RR = 1.27; p = 0.004), male suicides (RR = 1.29; p = 0.006), and secondary indices for both sexes.
Multivariate analysis
Data contained in Additional file
2 show the results of negative binominal regression modelling. There were no significant covariates in only one case (male suicide attempts). A two types of mass gatherings were included in the models as relevant factors — defeat of the local team at home, and mass events organized by new religious movements. They had significant regression coefficients in the models for three dependent variables — male suicides, male suicide attempts, and total suicide-related behaviour incidents.
In the male suicide model, mass events organized by new religious movements had a significant regression coefficient (beta = 0.255; p = 0.002) with the covariates of Sunday (negative) and Monday (positive).
The male suicide-related behaviour model showed significant effects of home defeats and mass events organized by new religious movements. The regression coefficients for defeats and new religious movement events were 0.371 (p = 0.002) and 0.251 (p < 0.001), respectively. This model also included the covariates of Sunday, Monday, and in-migration.
For the total suicide-related incidents, new religious movement events was a significant factor (beta = 0.187; p < 0.001) with the covariates of minimal daily temperature, Sunday, Monday, inflation index, and in-migration.
Conclusions
We found a significant increase in male and general suicide-related behaviour rates in an urban population after mass gatherings involving sub-populations of football fans and devotees of new religious movements amounting to only 1.6 and 0.3% of the population, respectively. It may suggest a causal link between such events and their participants’ suicide-related behaviour. We are inclined to interpret the findings in terms of the ‘broken-promises effect’ in the context of crowd behaviour. We believe that crowd behaviour in itself may not cause suicidal behaviour, yet it may exacerbate the ‘broken promise effect’ for its participants.
We suspect that the significance of the relationship between such events and population suicide-related behaviour rates may be contingent upon the relative size of the sub-population and its level of suicide-related behaviour. However, only further research may reveal the efficiency of our approach for assessing the level of suicide-related behaviour in a sub-population.
All the findings in this study can be explained largely within the framework of Gabennesch’s suicide theories of the ‘broken-promises effect’. However, we believe that suicide-related behaviour rates in an urban population after some types of mass gathering may also depend on the intensification of intra- and interpersonal conflicts, not only among the event’s participants, but also in their families and social environment.
Our study supports the view that ‘more studies are needed to understand the differing effect of different types of social events on suicidal behaviour among certain subpopulations and to develop suicide prevention approaches effective on both macro (societal) and the individual (psychological) levels’ [
7]. Our findings provide new evidence on how some forms of crowd behaviour may influence suicide-related behaviour risk. Otherwise, inadequate evaluation of these processes in some sub-populations may lead to a ‘broken-promise effect’ for the programmes that aim to reduce suicide rates in the general populations.
VSU: MD, PhD.
SNS: MD, Senior Psychiatrist of emergency medical aid.
YNS: Member of Dnipropetrovsk Municipal Expert Advisory Committee for Protection of Citizens’ Constitutional Rights.
EDP: PhD (Sociology, University of Michigan, 1996), director of the Laboratory for Comparative Social Research at the Higher School of Economics, Petersburg, Russia (
http://lcsr.hse.ru/en/), member of the Executive Board of the World Values Survey Association, the World Values Survey representative in Russia.
Acknowledgements
We would like to thank: A. Filatov, A. Nazarchuk, V. Vlasov, R. Demerdzi, and O. Tanana for their comprehensive support; V. Mikhailishyn for his administrative support and the data on religious mass events; D. Kabotyanski for informational assistance; E. Volkov for access to software; K. Dudko and S. Chub for data on concerts; K. Chebanov and A. Vasilenko for data on self-poisoning; A. Lipgart and Y. Apostolov for the translation; and special thanks to the Edanz company for the final editing of manuscript. We also thank the anonymous reviewers.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
VSU conceived of the study and its design, carried out statistical analysis and coordination, and helped draft the manuscript. SNS conceived of the study and interpreted the data. YNS conducted the acquisition and interpretation of the data. EDP conducted the regression analysis and made critical revisions. All the authors read and approved the final manuscript.