Background: Recent studies have reported changes in the time patterns of suicide, with conflicting findings regarding the direction of these changes: data from Italy were investigated to evaluate the influence of recent social and medicine-related changes on the seasonality of suicides in the country.
Methods: A total of 71,227 male suicides and 26,466 female suicides occurring in Italy from 1974 to 2003 were investigated with harmonic spectral analysis to extract their monthly seasonal dispersion by five-year intervals.
Results: The suicide rates of both males and females showed a rising trend, with an evident peak in the 1987-1994 period and a decrease thereafter. Seasonality of suicides, with a clear peak in spring as against the other seasons, accounted for a statistically significant proportion of total variance: around 40% among males and 39% among females. Seasonality did not change across time in a relevant way; however, an anticipation of the peak was observed in both males and females over time, with amplitude increasing or decreasing as a function of yearly suicide rates.
Limitations: Data could not be analysed according to age or to the method of suicide, since this information was not available across the whole time interval.
Conclusion: The seasonal effect on mortality by suicide is positively related to suicide rates, so much that changes in suicide rates over time correspond to changes in suicide seasonality.