Ketamine Infusion for Adolescent Depression and Anxiety

Inclusion: MDD Cohort: * Meet DSM-5 criteria for Major Depressive Disorder by structured interview (MINI-KID) * CDRS-R score \>40. * Failure to achieve remission with at least 1 adequate prior antidepressant trial (e.g. SSRI, SNRI, or TCA), meaning at least 8 weeks at therapeutic dosing, including at least 4 weeks of stable dosing. Anxiety Cohort: * Meet DSM-5 criteria for any of the following anxiety disorders: Social Anxiety Disorders, Generalized Anxiety Disorder, Separation Anxiety Disorder and/or Panic Disorder by structured interview (MINI-KID) * ADIS Clinical Severity Rating ≥4 (moderately severe) for any of the 4 included anxiety disorders * Failure to achieve remission with at least 1 adequate prior anxiolytic medication trial (e.g. SSRI, SNRI, or TCA), meaning at least 8 weeks at therapeutic dosing, including at least 4 weeks of stable dosing. * Failure to achieve remission with previous CBT or subject declines current CBT therapy Both cohorts: * Stable psychiatric medications and doses for the month prior to enrollment. Subjects may continue to engage in any ongoing psychotherapy. * Medically and neurologically healthy on the basis of physical examination and medical history. * Parents able to provide written informed consent and adolescents must additionally provide assent. Exclusion: * Current inpatient hospitalization or active suicidal ideation requiring referral for inpatient hospitalization for safety. * History of psychotic disorder or manic episode diagnosed by MINI-KID * History of substance dependence diagnosis by MINI-KID (excluding tobacco) or positive urine toxicology. * Pregnancy (urine pregnancy tests on the day of scans for menstruating girls). * Inability to provide written informed consent according to the Yale Human Investigation Committee (HIC) guidelines in English.