Ketamine Treatment of Youth Suicide Attempters for Fast Reduction of Severe Suicide Risk and Facilitation of Long-term Collaborative Clinical Engagement: A Randomized Placebo Controlled Trial Ketamine, an NMDA antagonist, has been shown to have rapid anti-suicidal effects. However, its safety and efficacy in special populations has not been investigated and documented. In the last decade there is an alarming increase of the number of suicide attempts in patients ages 15-24. Suicide is the second leading cause of death in this population. Patients with previous history of suicide attempt, are even in a higher risk category. The present study focus in this high risk group of suicide attempters. This will be a randomized controlled trial enrolling 140 youth between the ages 15-24 after a suicide attempt; patients will be randomized to receive Ketamine 0.5 mg/kg over 40 minutes or normal saline. Patients will receive their first ketamine infusion in the hospital (while admitted to an inpatient psychiatry unit).Patients will receive up to 6 ketamine infusions, or until for 3 consecutive sessions they report enduring decreased suicidal ideation. Patients will also participate in weekly sessions of Collaborative Assessment for the Management of Suicidality (CAMS), from the time they are admitted to the hospital and after their discharge until they are able to report no suicidal ideation for at least 3 consecutive outpatient sessions of CAMS. It is our hypothesis that patients in the Ketamine infusion+ CAMS group, will have a rapid improvement in the suicidality, be more engaged in the participation of CAMS, and in a 3 month follow-up period will have less number of suicide attempts, less number of admission to the ED secondary to suicidality compared to the Placebo+CAMS group. We expect that the rapid decrease of suicidality achieved in the ketamine + CAMS group, will lead to a more collaboration and engagement in their own ability to maintain their safety and be proactive in their treatment.