An Association between Initiation of Selective Serotonin Reuptake Inhibitors and Suicide - A Nationwide Register-Based Case-Crossover Study

Background: Treatment with selective serotonin reuptake inhibitors (SSRI) is one of the most common treatments for depression. It is however not clear whether or not there is an increased short-term suicide risk during initiation with SSRI. Methods: A register-based nationwide case-crossover study including 5,866 suicides, 1,698 women and 4,168 men, from the Death Register 2007-2010 in Sweden. SSRI initiation was defined as a dispensed prescription of SSRI within 28 days prior to the date of suicide with no previous dispensed prescription of SSRI within 4 months prior that prescription. The control period took place one year earlier. Odds ratio (OR) was estimated using conditional logistic regression. Result: During the 28 day period prior to suicide 48 women and 138 men were exposed to SSRI initiation (while not being exposed in the control period) and 22 women and 43 men were exposed in the control period (while not being exposed in the case period). The OR for suicide after initiation with SSRI was 2.7 (95% CI: 1.6-44) for women, and 4.3 (95% CI: 3.0-6.1) for men. The highest OR was found 8-11 days after initiation with SSRI 9.7 (95% CI: 3.0-31.7) for women and men combined. Conclusion: The main limitation in this study is confounding by indication, but the descriptive question is however not confounded by indication. Together with plausible biological mechanisms and previous clinical and epidemiological observations our findings, linking initiation of SSRI to increased short-term suicide risk, deserve further attention specifically in the clinical setting.