Selective serotonin reuptake inhibitor (SSRI) and serotonin-norepinephrine reuptake inhibitor (SNRI) medications are prescribed to approximately 2 to 3% of American children. Evidence suggests that these medications are beneficial for treating obsessive-compulsive disorder (OCD), anxiety disorders, and major depressive disorder. Following hearings in February and September of 2004, the FDA mandated Black Box warnings for all antidepressants, cautioning prescribers about the risk of treatment-emergent suicidal tendency in children and adolescents treated with these drugs. Although prescribing waned somewhat following the warning, many children continue to receive SSRIs and SNRIs for a variety of conditions that do not have empirically validated alternative treatments. Therefore, there is a pressing need to clearly understand the safety, tolerability, and effectiveness of SSRIs and SNRIs in children and adolescents. This study will identify variations in differentially expressed genes that may be involved in the development of suicidal events and certain behaviors in youth exposed to antidepressant medications.