Mounting evidence from a series of small clinical trials and case series suggests ketamine can have rapid and robust antidepressant(1), and possibly anti-suicidal effects(2) in patients who had not responded to standard treatment options. However, due to ketamine’s variable psychotomimetic effects in healthy volunteers and exacerbation of previously experienced positive symptoms in schizophrenic volunteers(3,4), patients previously experiencing psychotic features have been excluded from the reported studies and trials.
da Frota Ribeiro, C. M., Sanacora, G., Hoffman, R., & Ostroff, R. (2015). The use of ketamine for the treatment of depression in the context of psychotic symptoms. Biological Psychiatry. http://dx.doi.org/10.1016/j.biopsych.2015.05.016