Suicide and Season
Lucy Davidson, M.D., Ed.D.

We welcome spring as the harbinger of new life, yet spring represents a time of increased risk for completed suicide. This seems surprising, since the media often focus on suicide during the Christmas season. The percent of suicides occurring in December is even below the monthly average. All holidays can be painful times for survivors, who are reminded of the loss of the person they loved. However, particular seasons of the year -- not holidays -- are associated with more suicides.

Efforts to examine the monthly and seasonal fluctuations in suicide rates have reached slightly different conclusions according to the age group or geographic area studied and whether or not the study combined many years of data to avoid the possibility that a single year chosen might not represent a true pattern. Monthly percentages of suicides are adjusted for 30-day equivalents and compared statistically by fitting them to a periodic regression model. The seasonal pattern for suicide is highly significant with the rate of suicides being above average all spring and below average all winter. In the United States, April is usually the peak month and December is usually the trough. Suicide rates for persons aged 35 and older may peak again in the fall. Data from Italy have demonstrated seasonal variations between men and women as well as geographically within the country, but data from the United States do not.

Suicide attempts requiring hospitalization were recorded for nineteen years in Edinburgh. The frequency of attempts varied with the season, being higher in summer and lower in winter. December was the trough month.

Some authors suggest that the seasonality of suicide is associated with the seasonality of severe mood disorders, since the risk of suicide is increased among persons with these disorders. Others hypothesize that the increasing number of hours of daylight in spring affect suicide by lowering secretion of the hormone melatonin. Season related social changes may account for fall differences. We know that completed suicides represent the interaction of many biologic, situational, psychodynamic, and interpersonal factors. Seasonal fluctuations in many risk factors for suicide may account for aggregate seasonal variations in suicide rates, although the individual committing suicide may not share these particular risk factors. Research linking information about individual suicides and aggregate factors will clarify the causes of seasonal variations in suicide rates.