The investigators at the National Institutes of Health in Bethesda, Maryland have revealed that a single dose of the anaesthetic Ketamine is able to reduce depression in patients who show slight improvement with standard medications. The Ketamine starts working in less than two hours after it is consumed and the positive effects continue upto a week. The research, called the Hamilton Depression Rating Scale (HDRS), was carried out with 17 patients to study the effect of antidepressants (Ketamine). Seventy-one percent of patients were classified as treatment responders and 29 percent had little or no evidence of depression on day one after the ketamine dose. The treatment response was maintained for at least one week by 35 percent of patients. The authors note that the time that the anti-depressant response began and lasted was “nearly identical” for each subject.