Association of geomagnetic disturbances and suicides in Japan, 1999–2010
© The Japanese Society for Hygiene 2013
Received: 13 July 2011
Accepted: 16 July 2013
Published: 5 September 2013
Previous studies have shown a positive relationship between geomagnetic disturbances and an increased incidence of suicide. The Japanese suicide rate is the ninth highest in the world, but there have been no reports examining the relationship between geomagnetic disturbance and the number of suicides, and, therefore, this paper examines this relationship.
The number of Japanese suicides per month from January 1999 to December 2010 was obtained, and it was found that a total of 262,596 males and 102,539 females committed suicide during this period. To adjust the other factors which affect the number of suicides, a multiple linear regression analysis with backward elimination was carried out, with the monthly number of suicides as the response variable and the monthly mean K index value, monthly mean number of sunspots, monthly mean unemployment rate, proportion of elderly people (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h) as the explanatory variables.
In the multiple linear regression analysis for males, the monthly mean K index value was associated with the monthly number of suicides, but in females, the monthly mean K index value was not associated with the monthly number of suicides.
In this study, we generated a hypothesis that geomagnetic disturbances may trigger male suicides.
Suicide is an enormous public health problem throughout the world. Every year, about 800,000 to one million people commit suicide worldwide, making it a significant cause of death . Risk factors associated with completed suicides have been identified, such as psychiatric illness, hopelessness, previous suicide attempts, being widowed or divorced, living alone, having a recent adverse event, having severe anxiety, having a chronic medical illness, and having a family history of suicide attempts or completions . There have been some reports that environmental factors, such as electromagnetic fields [3, 4], latitude [5, 6], and season [5–7] were associated with suicides.
Articles investigating the relationship between changes in magnetic fields and suicides or depression
No. of suicides/admissions
January 1976–December 1986
1,042 male and 2,407 female admissions
Geomagnetic storms and the incidence of depression
There is statistically significant 36.2 % increase in male hospital admissions with a diagnosis of depressed phase, manic-depressive illness in the second week following such storms
Gordon and Berk 
January 1980–December 1992
1,200 males and 287 females
Geomagnetic storm activity and suicide rates
A significant correlation was found between the mean total number of suicides and the mean average storm activity during the same period. This correlation was true of both male and female suicides
Partonen et al. 
January 1979–December 1999
21,622 males and 5,847 females
The effect of solar radiation and geomagnetic activity on the frequency of suicides
High levels of solar radiation activity were associated with an increased risk of suicide, but the effect of geomagnetic activity was weak
Berk et al. 
January 1968–August 2002
51,845 males and 16,327 females
Geomagnetic storm activity and suicides
Suicide amongst females increased significantly in autumn during concurrent periods of geomagnetic storm activity. This pattern was not observed in males
Geomagnetic peaks and number of suicides
The geomagnetism peaks matched up with peaks in the number of suicides
January 1999–December 2010
262,596 males and 102,539 females
Geomagnetic activity and number of suicides
There was a statistically significant relationship found between the number of male suicides and the K index value
The K indices, devised by Bartels et al., provide an objective method of monitoring the effects of the solar wind and interplanetary magnetic field effects on the magnetic field of the Earth . It is routine to use them as indices of magnetic activity at permanent magnetic observatories and temporary stations . The basis of the K indices is the range of irregular variations in geomagnetic fields, which are measured for the two horizontal geomagnetic components, after eliminating so-called non-K variations . Sudden fluctuations can be observed during large geomagnetic storms for 1 ± 2 days . These are caused by the superimposition of equatorial ring current effects and auroral current effects, and generate field variations as large as 200 ± 300 nT at low latitudes and can exceed 1,000 nT at high latitudes . Partonen et al.  found a relationship between the smoothed monthly mean index of geomagnetic activity and the relative risk of suicide (n = 27,469) in Finland. Additionally, Gordon and Berk  found a relationship between the average storm activity and the number of suicides in South Africa. Shumilov looked at activity in the Earth’s geomagnetic field from 1948 to 1997 and found that it was grouped into three seasonal peaks every year: one from March to May, another in July, and the last in October . He also found that the geomagnetic peaks matched up with peaks in the number of suicides in the northern Russian city of Kirovsk over the same period . A large problem in most previous studies was that they only analyzed the relationship between geomagnetic disturbance and the number of suicides, but did not adjust for other variables.
In Japan, daily suicide data are not available from the Japanese national statistics website , but monthly suicides data are. If geomagnetic storms can desynchronize circadian rhythms and melatonin production, as has been reported previously , there is a possibility that the effect does not have a quick impact but, rather, a slow one. We, therefore, believe that an analysis using monthly suicides and geomagnetic activity data is meaningful. In addition, in Japan, about thirty thousand people commit suicide per year . The suicide rate in Japan is the ninth highest in the world , but there have been no reports examining the relationship between geomagnetic disturbance and the number of suicides, and, therefore, the present paper examines this relationship adjusted for other factors in order to generate a hypothesis.
Materials and methods
Monthly suicide data for the period from January 1999 to December 2010 were obtained from the Japanese national statistics website . A total of 262,596 males and 102,539 females committed suicide during this period. K index values were obtained from the website of the Magnetic Observatory, Japan Meteorological Agency . K index values from three observatories were obtained (Kakioka, Memanbetsu, and Kanoya) for each month from January 1999 to December 2010. The mean K index value was defined as the average value at the three observatories. Monthly mean unemployment rate (%) data were added to the analysis as an economic variable. Monthly mean unemployment rate data were obtained from the Japanese national statistics website . The monthly number of sunspots was added to the analysis because the number of sunspots has an 11-year cycle, which may have effects on economics . Otsu et al.  found, based on data from Japan between 1971 and 2001, a significant negative correlation between sunspot numbers and the unemployment rate. Data on the monthly number of sunspots from January 1999 to December 2010 were obtained from the Solar Influences Data Analysis Center . We obtained the monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h) data of each prefectural capital from January 1999 to December 2010 from the Japan Meteorological Agency website (Tokyo) . The national monthly mean values were defined as the average values at the 47 prefectures. The proportion of elderly people in the population (%) was defined as the number of elderly persons aged 65 years or older divided by the overall population in the same year. The number of elderly persons aged 65 years or older and overall population data from January 1999 to December 2010 were obtained from the Japanese national statistics website .
We conducted a regression analysis to examine the relationship between geomagnetic disturbance and the number of suicides, firstly carrying out a simple regression analysis. The monthly number of suicides was taken as the response variable, and the explanatory variable was the monthly mean K index value, monthly mean number of sunspots, monthly mean unemployment rate (%), proportion of elderly people (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), or monthly mean humidity (%), as well as the monthly mean day length (h). Secondly, to adjust the other factors which affect the number of suicides, we conducted a multiple linear regression analysis with backward elimination. The monthly number of suicides was taken as the response variable and the monthly mean K index value, monthly mean number of sunspots, monthly mean unemployment rate (%), proportion of elderly people in the population (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h) were the explanatory variables. Analyses were carried out separately for each gender. A P-value of 0.05 or less was taken to indicate statistical significance. Statistical analyses were performed using SAS version 9.2 (SAS Institute, Cary, NC, USA).
Monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly total day length (h) by calendar month in Japan
Monthly mean air pressure (hPa) ± SD
Monthly mean air temperature (°C) ± SD
Monthly mean humidity (%) ± SD
Monthly total day length (h) ± SD
1,011.7 ± 10.1
4.6 ± 3.3
65.8 ± 8.7
132.3 ± 49.8
1,011.6 ± 9.8
5.4 ± 3.5
64.8 ± 8.1
136.1 ± 42.2
1,009.5 ± 9.6
8.4 ± 3.1
62.8 ± 6.4
165.7 ± 34.9
1,008.0 ± 9.1
13.7 ± 2.6
63.0 ± 5.6
181.4 ± 35.2
1,005.3 ± 8.7
18.4 ± 2.1
67.2 ± 5.3
186.2 ± 34.4
1,002.8 ± 8.5
22.3 ± 1.8
73.0 ± 4.8
149.8 ± 32.3
1,002.1 ± 8.5
25.9 ± 2.2
75.0 ± 5.1
160.3 ± 56.5
1,003.7 ± 8.3
27.1 ± 1.8
72.4 ± 4.9
194.6 ± 41.8
1,006.6 ± 8.4
23.8 ± 2.1
72.3 ± 4.9
158.2 ± 30.0
1,010.4 ± 8.7
17.9 ± 2.5
70.1 ± 4.9
157.9 ± 27.6
1,012.3 ± 9.2
12.0 ± 3.0
69.0 ± 5.8
138.6 ± 33.0
1,012.0 ± 10.1
6.9 ± 3.3
67.2 ± 7.7
135.1 ± 47.0
Results of simple regression analysis
Results of simple regression analysis investigating the number of suicides against the monthly mean K index value, monthly mean sunspot numbers, monthly unemployment rate (%), proportion of elderly people in the population (%), monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h)
K index value
Unemployment rate (%)
Proportion of elderly people in the population (%)
Air pressure (hPa)
Air temperature (°C)
Day length (h)
Results of multiple linear regression analysis
Results of multiple linear regression analysis
K index value
Unemployment rate (%)
Air pressure (hPa)
Day length (h)
To adjust the other factors which affect the number of suicides, a multiple linear regression analysis with backward elimination was carried out, with the monthly number of suicides as the response variable and the monthly mean K index value, monthly mean number of sunspots, monthly mean unemployment rate, proportion of elderly people in the population, monthly mean air pressure (hPa), monthly mean air temperature (°C), monthly mean humidity (%), and monthly mean day length (h) as the explanatory variables. In the multiple linear regression analysis for males, the monthly mean K index value was associated with the monthly number of suicides, but in the multiple linear regression analysis of females, the monthly mean K index value was not associated with the monthly number of suicides. After adjusting for weather data, the unemployment rate, and sunspot numbers there was still a significant relationship between the K index and the number of suicides in males. On a simple linear regression, there was no significant relationship between the number of sunspots and the number of suicides; however, on a multiple linear regression analysis, there was a significant negative relationship. Similarly, while there was a significant positive correlation found on a simple regression analysis between the number of suicides and day length, there was no significance with multiple regression analysis, and the causes of this are unknown.
The monthly mean number of suicides was found to increase in March to June (Fig. 1c, d). These results correspond with previous reports showing the number of suicides to increase in spring [5–7]. We identified a relationship between geomagnetic disturbance and male suicides. This raises the question as to why males are influenced by geomagnetic disturbances but females are apparently not. Previous reports have not found gender differences [7, 9], but there is some evidence for such differences in the effects of various types of magnetic field [26–31].
Our results do not agree with some studies in which suicide numbers were found to be inversely related to geomagnetic activity [12, 13]. In a study, Stoupel et al. analyzed data from 1990 to 2002 . In 1991, Lithuania became independent from the Soviet Union. In 1995, Lithuania had the highest suicide rate in the world, at 45.6 per 100,000 people. Therefore, other factors such as changes in living conditions may affect the number of suicides.
Regarding the potential mechanism connecting geomagnetic disturbances and suicides, one hypothesis involves the effect of magnetic fields on opioid receptors. It has been shown that exposure to magnetic fields has opioid-mediated behavioral effects in rats, mice, land snails, and humans . As an example, exposure to pulsed magnetic fields was found to have significant antinociceptive or “analgesic” effects in Cepaea nemoralis, the land snail, demonstrated increased latency of response to a warmed (40 °C) surface . Attenuation of pulsed magnetic field-induced analgesia by naloxone, an opioid antagonist, as well as by mu and delta opioid receptor antagonists, provides further support for the role of opioids in the mediation of such analgesia [33, 34]. Furthermore, these effects were dependent on the presence of light, and were not present in the absence of light . Additionally, Galic and Persinger  examined whether geomagnetic disturbances are associated with pain thresholds by exposing adult mice to a hotplate paradigm once weekly for 52 weeks during the dark cycle. They found that hotplate latency was significantly and inversely correlated with daily geomagnetic intensity 3 days prior to testing. Higher levels of geomagnetic activity 3 days prior to a given hotplate trial tended to be associated with shorter response latencies in subjects, suggesting lower pain thresholds or less analgesia . In addition, there have been some reports that electromagnetic fields affect human pain thresholds . The administration of opioid analgesics in patients with known bipolar disorder provides an opportunity to observe some opioid-related mood-elevating changes . Therefore, there is a possibility that geomagnetic disturbances have an effect on opioid receptors and change people’s mood state.
One important limitation of our study was its ecological study design. Therefore, we cannot determine the causal relationship between geomagnetic disturbances and suicides. In addition, it is well known that geomagnetic disturbances vary with the season due to geophysical effects . Likewise, suicide rates vary with the season presumably due to sociological reasons . Thus, there will be a statistical association between geomagnetic disturbances and suicide even if there is no causal connection between them.
In this study, we generated a hypothesis that geomagnetic disturbances may trigger male suicides. In Japan, geomagnetic fields have been observed at some observatory stations, but there are no stations in prefectures with relatively high rates of suicide (e.g., Akita prefecture). For future research, we would like to measure the environmental magnetic fields in certain prefectures with relatively high rates of suicide and those with lower rates of suicide to verify the relationship between geomagnetic disturbance and the number of suicides.
We would like to thank Prof. Toshihiko Iyemori (Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University, Kyoto, Japan) for his insightful comments and suggestions.
Conflict of interest
Harue Tada received a research grant from the Ministry of Education, Culture, Sports, Science and Technology, with a Grant-in-Aid for Young Scientists (B), 21790581, 2009.
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