Seasonality of suicides with and without psychiatric illness in Denmark

Investigating risk of self-harm and suicide on anniversaries after bereavement by suicide and other causes: a Danish population-based self-controlled case series study

AIMS

To investigate mechanisms of suicide risk in people bereaved by suicide, prompted by observations that bereaved people experience higher levels of distress around dates of emotional significance. We hypothesised that suicide-bereaved first-degree relatives and partners experience an increased risk of self-harm and suicide around dates of (i) anniversaries of the death and (ii) the deceased's birthday, compared with intervening periods.

METHODS

We conducted a self-controlled case series study using national register data on all individuals living in Denmark from 1 January 1980 to 31 December 2016 and who were bereaved by the suicide of a first-degree relative or partner (spouse or cohabitee) during that period, and who had the outcome (any episode of self-harm or suicide) within 5 years and 6 weeks of the bereavement. We compared relative incidence of suicidal behaviour in (i) the first 30 days after bereavement and (ii) in the aggregated exposed periods (6 weeks either side of death anniversaries; 6 weeks either side of the deceased's birthdays) to the reference (aggregated unexposed intervening periods). As an indirect comparison, we repeated these models in people bereaved by other causes.

RESULTS

We found no evidence of an elevated risk of suicidal behaviour during periods around anniversaries of a death or the deceased's birthdays in people bereaved by suicide (adjusted incidence rate ratio [IRRadj] = 1.00; 95% confidence interval [CI] = 0.87-1.16) or other causes (IRRadj = 1.04; 95% CI = 1.00-1.08) compared with intervening periods. Rates were elevated in the 30 days immediately after bereavement by other causes (IRRadj: 1.95, 95% CI: 1.77-2.22).

CONCLUSIONS

Although people bereaved by suicide are at elevated risk of self-harm and suicide, our findings do not suggest that this risk is heightened around emotionally significant anniversaries. Bereavement care should be accessible at all points after a traumatic loss as needs will differ over the grief trajectory.

Timing of suicide in people with epilepsy: A population-based study from 18 states of the United States, 2003-2014

Suicide timing varies across several psychiatric disorders, which may share common underlying pathophysiological mechanisms with epilepsy. We investigated suicide timing in people with epilepsy. Using cross-sectional, population-based U.S. National Violent Death Reporting System data from 2003 through 2014 in 18 States, we identified 1310 suicides with epilepsy and 102,582 suicides without epilepsy among those 10 years and older. We compared patterns of suicide mortality ratios between those with and without epilepsy by month of year, week of month, day of week, time of day, and overall by age, sex, and race/ethnicity. As the suicide patterns seen among persons without epilepsy, suicides in persons with epilepsy occurred significantly more often during the morning, afternoon, and evening hours than at night in all subgroups except females. Compared to Sundays, suicides in persons with epilepsy were only significantly increased on Mondays and Tuesdays in those aged ≥45 years and only on Mondays in men. This pattern differs from persons without epilepsy whose suicides significantly increased on Mondays and significantly decreased on Saturdays in nearly all study subgroups. Suicides in persons with epilepsy did not exhibit the timing patterns of persons without epilepsy by week of month (significant decreases from the third to fifth weeks compared to the first week among those aged ≥45 years, males, and Non-Hispanic whites) and month of year (significant increases from January to November peaking from June to September compared to December in all study groups). Compared to the general population or people without epilepsy, previous and current studies suggest that in people with epilepsy, suicide timing differs from and suicide rates significantly exceed those in people without epilepsy. Preventing suicide in people with epilepsy should focus not only on the peak times of occurrence but also across all time periods.

Chris Cornell, the Black Hole Sun, and the Seasonality of Suicide

PURPOSE

Seattle-inspired rock and roll superstar Chris Cornell died by suicide in May 2017. In the northern hemisphere, May represents the peak of the widely replicated but still unexplained seasonal spring rhythm in suicide. Years earlier, Cornell had suffered openly from recurrent bouts of severe depression, and his early musical lyrics do indeed suggest an enduring sensitivity to the vicissitudes of depressed and suicidal states. Cornell's most famous song, Black Hole Sun, suggests a mixed mood state, the incidence of which also peaks in the spring. The present work explores Cornell's May suicide from a chronobiologic perspective.

METHODS

Review of Cornell's lyrics and literature on suicide.

RESULTS

Cornell's lyrics contain clear indicators of mixed depressive and seasonal imagery, highlighting 3 fundamental axioms of suicidology: (1) the yearly suicide rhythm peaks in May in the northern hemisphere, (2) mixed depressive states are particularly lethal, and (3) the suicide risk increases dramatically when recovering from depression and mood turns mixed.

CONCLUSIONS

Cornell, in his life and music, left us with a novel and important hypothesis about the spring seasonality of suicide, namely, that the yearly suicide risk becomes maximal when winter turns to spring and there emerges a deadly mixed mood state under a May photoperiod, i.e., the suicide risk is maximal when a Black Hole Sun occurs in May. It is hoped that Cornell's legacy and sensitive hypothesis inspire research into the etiology and treatment of the spring seasonality of suicide risk and mixed mood states.

LIMITATIONS

The Cornell hypothesis was formulated based in part on several speculative inferences regarding the course of his functioning just prior to his suicide.

The timing of general population and patient suicide in England, 1997-2012

BACKGROUND

There have been conflicting findings on temporal variation in suicide risk and few have examined the phenomenon in clinical populations. The study investigated seasonal and other temporal patterns using national data.

METHODS

Data on 73,591 general population and 19,318 patient suicide deaths in England between 1997 and 2012 were collected through the National Confidential Inquiry into Suicide examining suicide rates in relation to month of the year, day of the week, and individual days of national or religious significance.

RESULTS

Suicide incidence fell over successive months of the year and there was evidence of an overall spring peak. Monday was associated with the highest suicide rates and in the patient population this effect appeared to be more pronounced in those aged over 50 or those who lived alone. Suicide risk was significantly lower during Christmas, particularly for women. There was a peak in suicide on New Year's Day in the general population. Other 'special days' were not associated with a change in suicide incidence.

LIMITATIONS

We were limited to identifying associations between the variables investigated and were unable to explore causal mechanisms. We did not carry out comprehensive multi-variable adjustment in our regression models.

CONCLUSIONS

There is substantial seasonal and temporal variation in suicide deaths, and there appears to be some evidence in the clinical as well as the general population in England. Clinical services should be aware of the risk of suicide just after the weekend, especially in people who live alone, and the potential need for closer supervision during this period.

Do suicide attempts occur more frequently in the spring too? A systematic review and rhythmic analysis

BACKGROUND

Seasonal variations in suicides have been reported worldwide, however, there may be a different seasonal pattern in suicide attempts. The aim of this study was to perform a systematic review on seasonality of suicide attempts considering potential interfering variables, and a statistical analysis for seasonality with the collected data.

METHOD

Observational epidemiological studies about seasonality in suicide attempts were searched in PubMed, Web of Science, LILACS and Cochrane Library databases with terms attempted suicide, attempt and season. Monthly or seasonal data available were evaluated by rhythmic analysis softwares.

RESULTS

Twenty-nine articles from 16 different countries were included in the final review. It was observed different patterns of seasonality, however, suicide attempts in spring and summer were the most frequent seasons reported. Eight studies indicated differences in sex and three in the method used for suicide attempts. Three articles did not find a seasonal pattern in suicide attempts. Cosinor analysis identified an overall pattern of seasonal variation with a suggested peak in spring, considering articles individually or grouped and independent of sex and method used. A restricted analysis with self-poisoning in hospital samples demonstrated the same profile.

LIMITATIONS

Grouping diverse populations and potential analytical bias due to lack of information are the main limitations.

CONCLUSIONS

The identification of a seasonal profile suggests the influence of an important environmental modulator that can reverberate to suicide prevention strategies. Further studies controlling interfering variables and investigating the biological substrate for this phenomenon would be helpful to confirm our conclusion.

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.

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 risk in relation to air pollen counts: a study based on data from Danish registers

OBJECTIVES

Since the well-observed spring peak of suicide incidents coincides with the peak of seasonal aeroallergens as tree-pollen, we want to document an association between suicide and pollen exposure with empirical data from Denmark.

DESIGN

Ecological time series study.

SETTING

Data on suicide incidents, air pollen counts and meteorological status were retrieved from Danish registries.

PARTICIPANTS

13 700 suicide incidents over 1304 consecutive weeks were obtained from two large areas covering 2.86 million residents.

PRIMARY AND SECONDARY OUTCOME MEASURES

Risk of suicide associated with pollen concentration was assessed using a time series Poisson-generalised additive model.

RESULTS

We noted a significant association between suicide risk and air pollen counts. A change of pollen counts levels from 0 to '10-<30' grains/m(3) air was associated with a relative risk of 1.064, that is, a 6.4% increase in weekly number of suicides in the population, and from 0 to '30-100' grains, a relative risk of 1.132. The observed association remained significant after controlling for effects of region, calendar time, temperature, cloud cover and humidity. Meanwhile, we observed a significant sex difference that suicide risk in men started to rise when there was a small increase of air pollen, while the risk in women started to rise until pollen grains reached a certain level. High levels of pollen had slightly stronger effect on risk of suicide in individuals with mood disorder than those without the disorder.

CONCLUSIONS

The observed association between suicide risk and air pollen counts supports the hypothesis that aeroallergens, acting as immune triggers, may precipitate suicide.

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.

Prevalence of neurotic, somatoform and stress induced disorders in relation to the seasons and climatic factors during the 2010/2011

INTRODUCTION

Psychiatric disorders have been considered to have seasonal variation for a long time.

GOAL

The goal of this research is to study the admissions rate of neurotic and somatoform disorders, as well as stress induced disorder in relation to season and climatic factors during 2010/2011.

MATERIAL AND METHOD

The research was conducted at the Psychiatric Clinic, Clinical Center of University in Sarajevo. Randomly selected subjects (aged 5-89 years, 1316 males and 1039 females) N=2355, were interviewed by the Structural Clinical Interview (SCID) which generated DSM-IV diagnoses. In this retrospective-prospective, clinical-epidemiological study subjects were divided into groups according to type of disorders. Correlation between the impact of seasons and the rate of admissions to a Psychiatric clinic was analyzed. Certain data were taken from Federal Hydrometeorological Institute in Sarajevo about the climatic situation for period of the study.

RESULTS AND CONCLUSIONS

From the total number of subjects who were admitted to the clinic in the period of 2010/2011 the most common diagnoses were F10-F19, F20-F29, F30-F39, F40-F48, and the suicide attempts as the separate entity. It was found the correlation between certain seasons and the effects of the certain weather parameters at an increased admission rate of subjects with the neurotic, somatoform and stress induced disorders.

Seasonality of Chinese rural young suicide and its correlates

BACKGROUND

There had been few studies on seasonality of Chinese suicide especially for Chinese rural youths. In this research, we wanted to find the seasonal pattern and the relationship between personal and behavioral characteristics and seasonal variation of suicide.

METHOD

We examined Chinese rural young adults aged 15 to 34 years who died by suicide using Psychological Autopsy method to gather information from the informants of suicide victims. Altogether 330 suicide victims were collected among which 144 were female and 186 were male. The χ(2) test was used for comparison, and the multiple logistic regressions and Odds Ratios were adopted to analyze the seasonal preferences of suicide victims.

RESULT

Seasonal summer peak of suicide emerged in total population and in each subgroup. Four logistic regression models were constructed: in spring, six variables were included in the regression model, which were Gender (OR = 1.627), Pesticide Used (OR = 1.622), Life Events (OR = 2.764), Suicide Intent (OR = 1.641), Marital Status (OR = 0.574) and Family Conflicts (OR = 0.590); in summer, only Marital Status (OR = 1.927) was accepted; in autumn, four variables including Marital Problems (OR = 1.924), Trait Anxiety (OR = 1.758), Gender (OR = 0.518) and Religion (OR = 0.534) were retained; in winter, Pesticide Used (OR = 0.486) and Suicide Intent (OR = 0.614) were retained.

CONCLUSION

Seasonal variations of personal and behavioral characteristics, combined with social activities, might also play very important roles in suicide seasonality.

Animal model and neurobiology of suicide

Animal models are formidable tools to investigate the etiology, the course and the potential treatment of an illness. No convincing animal model of suicide has been produced to date, and despite the intensive study of thousands of animal species naturalists have not identified suicide in nonhuman species in field situations. When modeling suicidal behavior in the animal, the greatest challenge is reproducing the role of will and intention in suicide mechanics. To overcome this limitation, current investigations on animals focus on every single step leading to suicide in humans. The most promising endophenotypes worth investigating in animals are the cortisol social-stress response and the aggression/impulsivity trait, involving the serotonergic system. Astroglia, neurotrophic factors and neurotrophins are implied in suicide, too. The prevention of suicide rests on the identification and treatment of every element increasing the risk.

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 of suicide attempts: association with gender

Some studies suggest seasonality of suicide attempts in females, but not in males. The reasons for this gender difference remain unclear. Only few studies addressed the question whether gender differences in seasonality of suicide attempts reflect gender differences in the choice of method for suicide attempts, with inconsistent results. So, this study aimed to analyze the association of gender with seasonality in suicide attempts by persons living in two Northern Bavarian regions [city of Nuremberg (480,000 inhabitants) and region of Wuerzburg (270,000 inhabitants)] between 2000 and 2004. We addressed this question by focussing on the frequency of suicide attempts in relation to the seasons. The sample consisted of 2,269 suicide attempters (882 males and 1,387 females). The overall seasonality was assessed using the chi(2) test for multinomials. Moreover, the ratio of observed to expected number of suicide attempts (OER) with 95% confidence intervals within each season was calculated. As a result, overall distribution of suicide attempts differed significantly between seasons for women (chi(2) = 9.19, df = 3, P = 0.03), but not for men. Female suicide attempts showed a trough in the spring (decline compared to the expected value by 10%; OER = 0.9, 95% CI = 0.8-1.0). This trough was restricted to female low-risk suicide attempts (decline by 13%; OER = 0.87, 95% CI = 0.77-0.98). No seasonality was found for men. Seasonality of high-risk methods was more pronounced than that of low-risk methods; however, no significant gender differences were found concerning this aspect. The overall distribution of the sub-types of suicidal acts (parasuicidal gestures, suicidal pauses, suicide attempts in the strict sense) showed seasonality neither for males nor for females. Whereas seasonality was absent in male suicide attempters, the frequency of low-risk suicide attempts in females was 13.1% lower than expected in the spring.

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.

Seasonal spring peaks of suicide in victims with and without prior history of hospitalization for mood disorders

BACKGROUND

Seasonal spring peaks of suicide are highly replicated, but their origin is poorly understood. As the peak of suicide in spring could be a consequence of decompensation of mood disorders in spring, we hypothesized that prior history of mood disorders is predictively associated with suicide in spring.

METHODS

We analyzed the monthly rates of suicide based upon all 37,987 suicide cases in the Danish Cause of Death Registry from 1970 to 2001. History of mood disorder was obtained from the Danish Psychiatric Central Register and socioeconomical data from the Integrated Database for Labour Market Research. The monthly rate ratio of suicide relative to December was estimated using a Poisson regression. Seasonality of suicide between individuals with versus without hospitalization for mood disorders was compared using conditional logistic regression analyses with adjustment for income, marital status, place of residence, and method of suicide.

RESULTS

A statistically significant spring peak in suicide was observed in both groups. A history of mood disorders was associated with an increased risk of suicide in spring (for males: RR=1.18, 95% CI 1.07-1.31; for females: RR=1.20, 95% CI 1.10-1.32).

LIMITATIONS

History of axis II disorders was not analyzed. Danish socioeconomical realities have only limited generalizability.

CONCLUSIONS

The results support the need to further investigate if exacerbation of mood disorders in spring triggers seasonal peaks of suicide. Identifying triggers for seasonal spring peaks in suicide may lead to uncovering novel risk factors and therapeutic targets for suicide prevention.

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.

Reports of suicidality in clinical trials of montelukast

BACKGROUND

In recent years, a number of drugs and drug classes have come under scrutiny by the US Food and Drug Administration regarding suicidality (including suicidal behavior and ideation).

OBJECTIVE

We sought to perform 2 reviews (requested by the US Food and Drug Administration) of the number of events possibly related to suicidality reported in Merck clinical trials of montelukast.

METHODS

Method 1 was a descriptive review of clinical adverse experiences (AEs) from 116 studies (double-blind and open-label, adult and pediatric, and single- and multiple-dose studies) completed as of March 2008. Summaries were constructed from investigator-reported AE terms possibly related to suicidality (completed suicide, suicide attempt, and suicidal ideation) or self-injurious behavior. Method 2 used a retrospective adjudication of investigator-reported AEs and other events listed in the study database described as possibly suicidality-related adverse events (PSRAEs) in a prespecified set of 41 double-blind, placebo-controlled trials completed as of April 2008.

RESULTS

No completed suicides were reported in any study. For the descriptive review, 20,131 adults and children received montelukast, 9,287 received placebo, and 8,346 received active control; AEs possibly related to suicidality were rare and were similar between the montelukast and placebo or active-control groups. For the adjudicated review across 22,433 patients, there were 730 adjudicated events. In 9,929 patients taking montelukast, 1 PSRAE was identified (classified as suicidal ideation); none were identified in 7,780 and 4,724 patients taking placebo and active control, respectively.

CONCLUSIONS

Assessed by using 2 complementary methods, there were no reports of completed suicide, and reports of PSRAEs were rare in patients receiving montelukast and similar to those seen in control subjects.

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: relationship with the reason for suicide

AIMS

This study set out to test the hypothesis that the suicides that can be attributed to a psychiatric illness show a higher seasonality than the suicides due to any other reason.

METHODS

All the suicides registered in Italy from 1984 to 2000 (57,796 deaths by suicide: males = 41,741, yearly rate = 11.3 per 100,000; females = 16,055, yearly rate = 4.0 per 100,000) were analyzed with circular statistic techniques, based on the maximization of mean vector length method and on the Rayleigh test.

RESULTS

The suicides clearly attributed to a psychiatric illness were 35.0% among males and 51.3% among females. An economic reason for suicide was more frequently found among males; somatic illness or sentimental reasons were equally distributed in both sexes. The suicides attributable to a psychiatric illness showed a significantly higher seasonal unevenness than the suicides attributable to somatic illness and to sentimental or economic reasons.

CONCLUSIONS

The main drawback of this study is that psychiatric diagnoses were not formally assessed by a forensic specialist. However, it succeeded in showing that the dynamics of suicidal behaviour are not unilineal: suicides due to psychiatric or somatic illness mainly happen in spring/summer and those due to economic difficulties mainly in December. Patients with psychiatric and/or somatic illness should be more carefully followed in spring/summer.

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.