Patients must have a Diagnostic and Statistical Manual 5 (DSM-5) diagnosis of Major Depressive Disorder (MDD), as determined by a psychiatrist.

Patients must have a Diagnostic and Statistical Manual 5 (DSM-5) diagnosis of Obsessive Compulsive Disorder (OCD) as determined by a psychiatrist.

Patients must have a Diagnostic and Statistical Manual 5 (DSM-5) diagnosis of Post-Traumatic Stress Disorder (PTSD) as determined by a psychiatrist.

Patients must have a Diagnostic and Statistical Manual 5 (DSM-5) diagnosis of Somatoform Disorder as determined by a psychiatrist.

Patients must have a Diagnostic and Statistical Manual 5 (DSM-5) diagnosis of Anxiety Disorder as determined by a psychiatrist.

Ketamine, a N-methyl-D-aspartate (NMDA) receptor antagonist has been used for general anesthesia since the 1970s, however, reports and trials by the end of the twentieth century and onward using subanesthetic doses suggested robust and rapid antidepressant and anti-suicidal effects. Ketamine is available as a 50/50 racemic mixture of enantiomers (S)-ketamine and (R)-ketamine.Ketamine will be infused (slow IV infusions of ketamine (0.5 mg/kg) over 40 minutes) twice weekly over a period of 4 weeks) Ketamine will be given in intranasal spray twice weekly over a period of 4 weeks Ketamine will be given orally (solution 2.0mg/kg, 2.5mg/kg) twice weekly over a period of 4 weeks.

Incidence of adverse events will be assessed by Clinician-Administered Dissociative Symptoms Scale (change from baseline to each measure). Higher values represent a worse severity, but not necessarily outcome. The Clinical-Administered Dissociative Symptoms Scale has 23-items based on dissociative symptoms during the assessment. Each item is scored 0 (normal) to 4 (severe symptoms) with overall score ranges from 0 (normal) to 92 (severe symptoms). Total number of assessments:18 times

Incidence of adverse events will be assessed by 4-items positive symptoms subscale of Brief Psychiatric Rating Scale (change from baseline to each measure). Higher values represent a worse severity but not necessarily outcome. The 4-item positive symptoms subscale of Brief Psychiatric Rating Scale has 4-items based on conceptual disorganization, suspiciousness, hallucination and unusual thought content. Each item is scored 0 (normal) to 6 (severe symptoms) with overall score ranges from 0 (normal) to 24 (severe symptoms).

Incidence of adverse events assessed by body temperature (oral measurement) in Celsius degree - change from baseline to each measure. A normal range is from 36.2 to 38.0 Celsius degrees; measurements beyond those ranges are clinically significant. The total number of measurements: 44 times

Incidence of adverse events assessed by blood pressure (after the participant has rested for at least 5 minutes) in mmHg - change from baseline to each measure. A normal range for systolic blood pressure is from 90 to 140 mmHg, for diastolic blood pressure is from 50 to 90 mmHg; measurements beyond those ranges are clinically significant.

Change in severity of depression symptoms from baseline to each measure. Higher values represent a worse severity, but not necessarily outcome. The MADRS has 10-items which are based on mood symptoms over the past 7 days. Each item is scored 0 (normal) to 6 (severe depression) with overall score ranges from 0 (normal) to 60 (severe depression).