AbstractObjectiveTo evaluate the effectiveness of the IDF Suicide Prevention Program, implemented since 2006.DesignQuasi-experimental (before and after) cohort study.ParticipantsTwo cohorts of IDF mandatory service soldiers: the first inducted prior to (1992–2005,n= 766,107) and the second subsequent to (2006–2012,n= 405,252) the launching of the intervention program.ExposureThe IDF Suicide Prevention Program is a population-based program, incorporating: reducing weapon availability, de-stigmatizing help-seeking behavior, integrating mental health officers into service units, and training commanders and soldiers to recognize suicide risk factors and warning signs.Main outcome measureSuicide rate and time to suicide in cohorts before and after exposure to the Suicide Prevention Program.ResultsTrend analysis showed lower suicide rates in the cohort after intervention. The hazard ratio for the intervention effect on time to suicide was 0.44 (95% CI = 0.34–0.56,P< .001) among males. Lower risk was associated with: male gender; born in Israel; higher socio-economic status; higher intelligence score; and serving in a combat unit (HR = 0.43: 95% CI = 0.33–0.55).ConclusionsThere was a 57% decrease in the suicide rate following the administration of the IDF Suicide Prevention Program. The effect of the intervention appears to be related to use of a weapon, and being able to benefit from improved help-seeking and de-stigmatization. Future efforts should seek to extend the program's prevention reach to other demographic groups of soldiers. The success of the IDF program may inform suicide prevention in other military organizations and in the civilian sector.