With this the investigators attempt to discover 1) whether suicidal ideation or behavior is associated with differences in the expression of specific miRNAs, 2) whether anti-suicidal/antidepressant effects of ketamine is associated with miRNAs changes, and 3) whether miRNA/mRNA-regulatory pathways contribute to suicide pathogenesis and treatment response. Our study will provide a novel avenue for the development of miRNAs as ''molecular tool'' to identify suicidality and treatment response and in generating target based therapies to treat this devastating disorder.