SYNCHRONIZED ANNUAL RHYTHMS IN VIOLENT SUICIDE RATE, AMBIENT-TEMPERATURE AND THE LIGHT-DARK SPAN

To investigate whether violent and nonviolent suicide and homicide are related to atmospheric or geomagnetic activity, we investigated the r elationships between weekly number of suicides or homicides for all Be lgium for the period 1979-1987, and ambient temperature, relative humi dity, air pressure, hours of sunlight and precipitation per day, wind speed and geomagnetic index. The occurrence of violent suicide was sig nificantly and positively related to ambient temperature, sunlight dur ation, an increase in temperature over the few past weeks, and negativ ely to relative humidity. Higher ambient temperature and an increase i n air temperature over the few past weeks were the most significant cl imatic predictors of violent suicide rate. A highly significant common annual rhythm with a common acrophase of 190 degrees was detected in violent suicide rate, ambient temperature and sunlight duration. No si gnificant time-relationships between nonviolent suicide or homicide an d any of the weather variables were found. It is concluded that i) vio lent suicide may be related to short-term fluctuations in the weather and in particular to temperature; and ii) the annual rhythm in violent suicide may be synchronized by the annual rhythms in ambient temperat ure and light-dark span.