It has often been stated that there is a seasonal variation in suicidal deaths, with more occurring in the spring than at other times of the year. The analysis of this phenomenon has, however, remained at a relatively crude level. For example: (1) Recent data (Dublin, 1963) indicate that the pattern is not simple. There appears to be a subsidiary peak in suicidal deaths in the early winter in the U.S.A. (2) Investigators have not investigated whether the seasonal variation is found more strongly in some subgroups of the population than in others. (3) Investigators frequently omit to carry out statistical tests of significance on their data. The present study sought to investigate the seasonal variation in suicidal deaths, taking these considerations into account.
The combination of statistical tests of significance