Seasonality in severity of depression: relationships to suicide and homicide occurrence

Abstract

Some previous studies have reported seasonal or monthly variations in the occurrence of depressive syndromes. The present study was carried out in order to investigate seasonality in severity of depression. Toward this end, the authors measured the Zung Self-Rating Depression (ZD) and Anxiety (ZA) Scales scores in 104 consecutively admitted depressed patients between November 1983 and April 1985. The data were analyzed by means of spectral analysis of a single time series. Up to 47.9% of the variance in the weekly average of the ZD scores could be explained by two significant rhythms of 51 (circannual) and 7 weeks. Peaks in ZD scores were observed in April-May, with lows occurring in August-September. Up to 30.8% of the variance in the weekly average of ZA scores was explained by a circannual rhythm. Our results show that there is a true seasonality in the severity of illness of depressed subjects. There were significant correlations between the weekly average in severity of illness and the chronograms of suicide (positively) and homicide (negatively) occurrence in Belgium.

Occurrence of suicide and seasonal variation

“…A Spanish report comparing warm to cold months between 1981 and 1985, showed higher rates for the warm season 4 . In Belgium, the same pattern has been demostrated 12 . With reference to the Southern Hemisphere, in 1937, an Argentinean group from the city of Buenos Aires reported an increase in the occurrence of suicide in spring, as quoted by Asberg 1 .…”

“…A cyclic occurrence of depressive episodes in affective disorders in spring and autumn was reported in several studies 3,7,9,23 . Recently, human biometeorological research has revealed the effects of seasonality on the affective state of normal men 12 and on the occurrence of affective disorders, seasonal affective disorders, suicide and neurotic complaints 3,6 , thus relating severity of depression or specific depressive symptoms to an increase in the risk of suicide. It is also known that both hospital incomes and electro-convulsive therapy for depressive patients are higher in autumn and spring.…”

“…A clear correlation has been determined as between psychiatric hospital admission and season 7,9 . Eastwood & Peacocke 6 and Maes et al 12 , were able to determine a clear correlation between the seasonal pattern in severity of depression and the occurrence of suicide and homicide, suggesting that the severity of depression in the depressed population may explain the occurrence of suicide. In Chile, an early work during the 70s reported a higher suicide rate during spring time with the lowest rate occurring during winter time 22 .…”

Changes in Severity of Allergy and Anxiety Symptoms Are Positively Correlated in Patients with Recurrent Mood Disorders Who Are Exposed to Seasonal Peaks of Aeroallergens

“…Worldwide, a peak in suicide in the spring is consistently observed in epidemiologic research studies (2)(3)(4)(5)(6)(7)(8). In the fall, a second, smaller peak in suicides has also been observed, although it has been less well replicated (7,(9)(10)(11)(12).…”

Influence of Method on Seasonal Distribution of Attempted Suicides in Italy

“…In recent years, a clear seasonal variation in the occurrence of episodes of mental disorder has been observed in many countries, Italy included. This had led to the suggestion that such a factor could contribute to the seasonal distribution of suicides [7,22,27,[43][44][45]. Mood disorders (which account for most suicides) often show particularly clear seasonality in their occurrence.…”