A case-crossover study of acute alcohol use and suicide attempt

OBJECTIVE: Several studies have shown that acute alcohol use is associated with suicidal behavior, but the magnitude and nature of the relationship remain unclear. We report a study on the impact of acute alcohol use on suicide attempts treated in the emergency room (ER) using the case-crossover design. METHOD: Seven ER studies carried out in the United States, Canada, Mexico and Australia from 1984 to 1996 with probability samples and similar methodology were merged yielding a total of 102 suicide attempters (overall 52% were male and 59% under 30 years of age). RESULTS: Thirty-six patients reported alcohol use within 6 hours prior to the suicide attempt. When usual alcohol consumption during the past 12 months served as the control value, the estimated relative risk (RR) for patients who reported alcohol use within 6 hours prior to the suicide attempt was 9.6 (95% confidence interval: 5.7-16.3). Although the prevalence of alcohol use differed by sex, there was no statistically significant difference in the estimated RRs (RR = 13.6 men and RR = 5.3 women, p = 0.11 for the heterogeneity test). CONCLUSIONS: A positive association was found between alcohol use 6 hours prior and suicide attempts in 102 ER cases in four countries. The case-crossover methodology is well suited to studies for which an external control group is not easily obtainable.