Environmental factors and suicide behavior in human being

Suicide is influenced by various environmental factors. This is most clearly manifested in the repeatedly confirmed seasonality of suicidal behavior - the presence of a spring-summer and less pronounced autumn peaks. This phenomenon can be associated with both biological (thermoregulation, insolation, daylight hours), and social factors, which are also usually confined to natural seasonality. Variations of suicides are accompanied (and partly explained) by seasonal exacerbations of mental disorders, aggressive behaviors enhancement and psychological conditions associated with the change of seasons. The hypothesis that the seasonality of suicide will gradually diminish due to urbanization does not seem to be confirmed by many studies. The human beings, despite their power over nature, remain dependent on a variety of biological rhythms (circadian, infradian and ultradian) which is reflected, among other effects, in the frequency of suicides during each month, weekdays and across the day. The objective verification of various suicidal fluctuations is a difficult statistical task, and the use of different methods of analysis, sample differences and geographical variations lead to heterogeneous results. Besides, cyclic variations are impacted by aperiodic weather phenomena and various physical factors of the external environment, both natural (helio-geomagnetic disturbances, cosmic weather), and technogenic (artificial electromagnetic fields of various characteristics). It is quite probable that one of the provoking factors may be the infrasound associated with extreme weather patterns. Studies of the relationship between the frequency of suicide and the lunar cycle are controversial. A number of studies evaluating the impact of Chernobyl catastrophe and other radiation accidents have found an increase in the incidence of suicides due to the combined effect of radiation and psychological factors associated with the subjectively perceived danger of ionizing radiation. Other environmental pollutants including smog and degradation of the environment as a whole accompany elevated levels of suicide. A generalizing scheme of the pathogenesis of cyclic and aperiodic variations of suicide frequency under the influence of environmental factors is proposed. It posits stress-vulnerability as the central phenomenon, while various environmental factors act as additional stressors leading to exacerbations of chronic somatic diseases and psychiatric disorders.