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The rate of suicide varies according to the season but also depends on factors such as the age of the person. Researchers recently reviewed the literature in this regard and confirmed that there is virtually always a peak in suicides in the spring among all subgroups. Then they broke down the data by socioeconomic status, marital status, gender, age, methods of any prior attempt to commit suicide, concurrent medical and psychiatric diagnoses, and even month or birth. The researchers believe that by being able to better sort out these factors it will lead to better measures for prevention of suicide. At No Fallen Heroes we are dedicated to the reduction and elimination of veteran suicide. As such we pay attention to attempts like this to better understand veteran suicide with an eye toward eventual elimination of unnecessary deaths of our military heroes.

Seasonality of Suicide Changes Over Time

Although the springtime peak in suicides has been a factor for a long time it appears to be diminishing in amplitude in recent years. This is especially the case in industrialized nations in the West. Nevertheless, the researchers looked at factors that correlate with springtime suicide attempts including temperature, the amount of sunlight, air pollutants, pollens and other allergens, parasites, viruses, and exposure to chemicals, all of which have been associated to some degree with the risk of suicide. An additional factor was mood disorders associated with lack of sunlight.

Seasonality of Suicide Changes Over Time
Seasonality of Suicide Changes Over Time

Environmental Factors Related to the Seasons and Suicide

Because environmental factors can affect human behavior temperature, rainfall, sunshine, chemical pollutants, infectious agents such as protozoa, bacteria, viruses, and allergens we considered as reasons for suicide rate peaks in fall and spring. One finding that may be pertinent is that the climate-related peaks in suicide are most highly related to attempts by violent means.

Although one might assume that seasonal affective disorder caused by lack of sunlight would increase suicide rates it turns out that the intensity of sunlight may be positively related to suicide attempts. Outdoor workers have higher suicide rates than indoor workers and suicide rates are higher in rural settings than in urban settings. One report indicated that suicide peaks during times of longer day lengths (May to July in the Northern Hemisphere. Part of this puzzle is that the effect is more pronounced at higher latitudes (Greenland vs Southern Finland).

Environmental Factors Related to the Seasons and Suicide
Environmental Factors Related to the Seasons and Suicide

A study done in Brazil showed higher suicide rates when the temperature was highest (December and January in the Southern Hemisphere) which is also when the days are longest but not by much in areas near the equator. They reported that as the temperature went up by 1 degree Celsius (1.8 degrees Fahrenheit) suicide rates increased by 1.4%. In addition, meteorological factors such as humidity and storms related to temperature changes also added to suicide risk.

Although the spring peak in suicides is found across many nations (28 in one study) the magnitude of the effect varied. For example, the increase in the suicide rate in the spring was nearly nine times greater in Portugal than in Canada.

Allergens and Suicide Rates

For years it has been known that allergy flareups have an effect on suicide rates. Peaks in tree pollen in the spring, grass pollen in the summer, and ragweed in the fall are all observed. Researchers looked at chemicals produced in the body as part of reactions to allergens and found that chemicals called Th2 cytokines are produced in allergic reactions and also induce anxiety, decrease social interactions, and increase aggressiveness. The researchers also speculate that worsening of allergy symptoms is likely to increase depression in those prone to it and impulsivity in those prone to it in each case increasing the risk of suicide. The researchers go on to explain the complicate physiology of this risk but the bottom line is that chemicals produced in allergic reactions seem to have an effect of increasing the risk of suicide.

Unlike allergies, pollution can occur at any time of the year. Studies have shown that ER visits for depression spike after two successive days of high pollution. Since depression is one of the major risk factors for suicide this links pollution and suicide risk. The studies in this regard did not include concomitant assessment of allergies.

A Mix of Factors Affect Suicide Risk

The data on how seasons, temperature, sunlight, pollen, pollutants affect the risk of suicide are interesting and, hopefully, useful in helping reduce the incidence of suicide. What is important to consider is that a mix of factors bear on the risk of suicide and very commonly one risk factor that comes and goes makes its effect by changing the severity of another constant risk factor. The bottom line is that dealing as effectively as one can with constant risk factors like PTSD and depression will make additive factors less of an issue.

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