Background: Violence is an urgent problem concerning society as a whole. If chronobiological changes of human aggressiveness existed, it would be possible to foresee them and when an increased incidence is expected it would be perhaps possible to use preventive measures.
Methods and results: The author processed data on 2447 aggressive acts of violence and 1028 completed suicides (aggression against oneself) on the territory of the former South Moravian region according to a weekly, annual and lunar rhythm and in relation to sudden climatic changes. The most remarkable finding is that the impulsive bodily harm (usually without economic or sexual motivation) is very closely associated with sudden climatic changes, while burglary and rape do not depend on climatic changes and their frequency correlates with the semilunar rhythm (there are two peaks during lunation), similarly as the frequency of sudden cardiovascular deaths. In suicides the frequency changes, with certain exceptions, similarly as the incidence of impulsive intentional bodily assault. In general close to the phase of full moon aggressiveness is significantly reduced and not increased, as was and still is believed by mistake, based on few observations and impressions.
Conclusions: The assessed periodicities differentiate types of aggressive behaviour, prove the possibility of prediction of an increase of the mean incidence and provide thus a basis for estimation of the time and type of increased aggressiveness. It is thus possible to introduce preventive measures.