Evaluation of circadian, circaseptan, and circannual periodicity of attempted suicides.

A retrospective investigation has been carried out on the incidence of attempted suicides registered at the Fatebenefratelli Hospital in Milano, during the span from June 27, 1978 to November 11, 1980. On a total of 451 cases, the age, sex, hour, day of the week and date of the attempted suicide have been recorded for each single case. The cosinor analysis for tau = 24 h has shown that a circadian periodicity is statistically significant both for the total of men (phi =-265 degrees +/- 17) and for the total women (phi =-285 degrees +/- 13), with p less than 0.01. The maximum incidence occurs during the later afternoon (approximately between 1700 and 1900). The results are similar to those obtained for the younger subjects only (up to 22 years), while for the following range of age, (22 to 40 years), and after 40 years, the rhythm is not so well demonstrable. As regards the circaseptan rhythm, it is quite evident for women, both up to 22 years (maximum incidence on Friday) and between 23 years and 40 years (maximum incidence Thursday), and from 40 years onwards, but it is not demonstrable for men. A circannual rhythm is demonstrable, on the contrary, both for men and women: the maximum incidence is in May for men and in February for women. Language: en