Natural Medicines in Schizophrenia: A Systematic Review

Abstract

Background: Despite progress in treatment options in the last century, the results of pharmacological treatment of schizophrenia are frequently unsatisfactory. Therefore some patients use natural medicines, although it is unclear whether natural medicines are effective and safe. We assessed the evidence for natural medicines with and without antipsychotics in treating symptoms or reducing side effects of antipsychotics in schizophrenia. Methods: A systematic review until April 2013. Only RCTs with a Jadad score of 3 or higher were included. Results: 105 RCTs were identified. Evidence was found for glycine, sarcosine NAC, some Chinese and ayurvedic herbs, ginkgo biloba, estradiol and vitamin B6 for improving symptoms of schizophrenia when added to antipsychotics (glycine not when added to clozapine). Inconclusive or no evidence was found for omega-3 fatty acids, D-serine, D-alanine D-cycloserine, B vitamins, vitamin C, dehydroepiandrosteron (DHEA), pregnenolone (PREG), inositol, gamma-hydroxybutyrate (GHB) and des-tyrgamma endorphin when added to antipsychotics. Omega-3 fatty acids without antipsychotics might be beneficial in the prevention of schizophrenia. In one large study, ayurvedic herbs seemed effective without antipsychotics. Other agents without antipsychotics (vitamin B3, vitamin C sarcosine, glycine, Protilerin) were not effective or had only been tested in single or small trials. Ginkgo and vitamin B6 seemed to be effective in reducing side effects of antipsychotics (tardive dyskinesia and akathisia). The evidence for reducing side effects of antipsychotics by omega-3 fatty acids, melatonin and DHEA appeared to be inconclusive. All natural agents produced only mild or no side effects. Discussion: High-quality research on natural medicines for schizophrenia is scarce. However, there is emerging evidence for improved outcome for glycine, sarcosine, NAC, some Chinese and Ayurvedic herbs, ginkgo biloba estradiol and vitamin B6, all with only mild or no side effects. Most study samples are small, the study periods are generally short, the studies only cover a modest part of the world's population and most results need replication.