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.
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 depression with winter. Harsh weather increases the prevalence of diseases such as pneumonia and hypothermia, which have mainly been from the minimal amount of sunlight in the winter time. In turn, this notion is indicative of the winter season having a general association 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.”
The Center 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 summer and spring. F. Stephen Bridges asserts that there is “a high incidence in early spring (April and May) and…also a low incidence in winter” of suicides 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). From 1980 to 1990, “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”. For the 1990–2000 decade, “the significant seasonal rhythm were explained in 63% of the total variation.”
According to Bridges, recent research from industrialized countries (including Finland, Sweden, Australia and 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#Seasonal suicide variations in the southern hemisphere. Studies in Brazilhave 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 Parana and Santa Catarina states, and in early summer (January) for women of Parana state.”
Eleni Petridou, a professor of Preventive Medicine & Epidemiology, led an international study on seasonal effects on suicide rates that involved twenty countries. The results 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 J. Edwards and F. Whitlock found a “spring peak in the number of suicides committed in Brisbane, Australia, but the results were not statistically significant…and thatDublin 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.”
