Positive antidepressant effects of ketamine are derived from studies using a dosage of 0.5 mg/kg or its oral/sublingual equivalent, not microdosing.

“All of the positive effects on depression that I've talked about during this episode are gleaned from studies where people used this half milligram per kilogram dosage of ketamine or it's equivalent by way of some other route of administration not injected but oral or sublingual”