There is a growing body of clinical evidence that has shown how ketamine works to produce antidepressant effects in those with treatment-resistant depression (TRD). These studies have used a common subanesthetic dose of 0.5 mg/kg over a period of 40 minutes when administered through an IV. An outpatient study from 2018, published in Molecular Psychiatry, recently added onto this body of research in order to find the optimal dose for antidepressant effects in those with TRD. They found that single IV doses of ketamine of 0.5 mg/kg and 1 mg/kg proved to be more effective than an active placebo in reducing depression over a 3-day period.