Research on seasonal effects on suicide rates suggests that the prevalence of suicide is greatest during the late spring and early summer months, despite the common belief that suicide rates peak during the cold and dark months of the winter season. From both a behavioral and a biological standpoint, the reasons for this are unclear, but associations between seasonality and other possibly related phenomena have been found.
General effects The Centers for Disease Control and Prevention and the National Center for Health Statistics report that suicide rates in the United States are lowest during the winter months and highest in the spring and summer. Stephen Bridges asserts that there is "a high incidence in early spring (April and May) and also a low incidence in winter" of suicide rates. Bridges's study focused on seasonal effects on suicide risk by examining the monthly distribution of suicides in the 1970s, 1980s, and 1990s via a "harmonic time series model" with six observable harmonic cycles within each consecutive year. The results show a consistent pattern of suicide risk with most suicides occurring in the spring/summer and the fewest during the winter months. Specifically, Bridges found that in the 1970s "about 47% of the total variances can be explained by the seasonal components" within that given decade (with more suicides in spring/summer). In the 1980s, "the seasonal component of suicide incidence for the time period 1981 through 1990 is clearly significant and records about a 27.7% increase in seasonal contribution by comparison with the previous period". In the 1990s, "the significant seasonal rhythm were explained in 63% of the total variation". According to Bridges, recent research from industrialized countries (including Finland, Sweden, Australia, New Zealand, England, and Wales) has provided enough information to show a decrease in seasonal effects on suicide rates over the past few decades. In the case of Greece, seasonal variations in mortality from suicide are "more frequent during the spring and summer months…but [have] no regular annual rhythm". The Greek researchers proposed that "the seasonal variation of suicide follows more closely to the seasonal variation of sunshine, rather than the corresponding variation of temperature". Few scientific assessments have focused on seasonal suicide Epidemiology of suicide variations in the southern hemisphere. Studies in Brazil have shown that "the peak number of suicides occurred in spring (November) in men and women of Rio Grande do Sul state and in men of Paraná and Santa Catarina states, and in early summer (January) for women of Paraná state." One international study on seasonal effects on suicide rates involving 20 countries showed an early summer peak in suicides. She concluded that "seasonal variation in suicide incidence could be explained by the increase in sunshine in summer months because of a relationship between sunshine, high temperatures, and suicide rate". Australian researchers found a "spring peak in the number of suicides committed in Brisbane, Australia, but the results were not statistically significant…and that Dublin reported the incidence of suicide varied according to seasons in the northern hemisphere". French sociologist Émile Durkheim had found similar results, reporting that more suicides occurred in the spring than in the summer. Rather than emphasizing the role of nature, Durkheim interpreted the seasonal variation in sociological terms; he wrote that most suicides took place in the spring because "everything begins to awake; activity is resumed, relations spring up, interchanges increase. In other words, it is the density of human interactions, and not the environment that caused higher incidence of suicide in spring or summer".
Popular belief Many people believe that suicide rates peak during the winter months. Intuitively, this makes sense given the existence of seasonal affective disorder and the tendency to associate winter with depression. Weather in the colder season increases the prevalence of afflictions such as pneumonia and hypothermia, which largely proceeds from the minimal amount of sunlight exposure in the wintertime. As winter is popularly associated with a decrease in sunlight and an uptick in distempers, so it is by extension with suicide rates. Some also believe that "holiday cheer amplifies loneliness and hopelessness in people who have lost loved ones, or who have high expectations of renewed happiness during the holiday season, only to be disappointed".
Related factors Suicide attempts as well as other related behaviors and thought processes can be analyzed either exogenously (within the boundaries of social and economic elements) or endogenously (demographic, pathological, clinical, and seasonal aspects).
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