ABSTRACT
Depressive illness and related suicide attempts have been reported to have seasonal variation, possibly related to weather. This study sought to determine the effects of weather and time of year on suicide attempts by carbon monoxide (CO) poisoning. Cases of patients in western Washington State attempting suicide by CO poisoning and referred to a regional hyperbaric oxygen treatment center from 1981-1995 were reviewed retrospectively. Information from the National Climatic Data Center was used to compare date of treatment to local weather data on the day of attempted suicide and on each day of the preceding week. The study population consisted of 264 patients attempting suicide by CO poisoning on 251 days of the 15-yr period. Mean and total precipitation in the preceding 7 days strongly correlated with attempted suicide rate, with incident rate ratios ranging from 1.75 to 2.77 and 1.14 to 1.75, respectively (P values <0.05). A decrease in minimum daily temperature also correlated with attempted suicide rate. No other weather variables showed significant correlation with dates of CO suicide attempts. February, March, and October were seen to be separate factors related to a higher incidence of attempted suicide by CO poisoning. Precipitation in Seattle, change in minimum temperature, and month of the year correlated with the regional incidence of suicide attempts with CO poisoning.
