- Background: Vitamin B 6 , or pyridoxine, plays an intrinsic role in the synthesis of certain neurotransmitters that take part in development of psychotic states. Several reports indicate that vitamin B 6 may be a factor in a number of psychiatric disorders and related conditions, such as autism, Alzheimer's disease, hyperactivity, learning disability, anxiety disorder, and depression. Moreover, there are anecdotal reports of a reduction in psychotic symptoms after vitamin B 6 supplementation of psychopharmacologic treatment of patients suffering from schizophrenia or organic mental disorder. The aim of this study was to examine whether vitamin B 6 therapy influences psychotic symptoms in patients suffering from schizophrenia and schizoaffective disorder. Method: The effects of the supplementation of vitamin B 6 to antipsychotic treatment on positive and negative symptoms in 15 schizophrenic and schizoaffective patients (DSM-IV criteria) were examined in a double-blind, placebo-controlled, crossover study spanning 9 weeks. All patients had stable psychopathology for at least 1 month before entry into the study and were maintained on treatment with their prestudy psychoactive and antiparkinsonian medications throughout the study. All patients were assessed using the Positive and Negative Syndrome Scale (PANSS) for schizophrenia on a weekly basis. Patients randomly received placebo or vitamin B 6 , starting at 100 mg/day in the first week and increasing to 400 mg/day in the fourth week by 100-mg increments each week. Results: PANSS scores revealed no differences between vitamin B 6 - and placebo-treated patients in amelioration of their mental state. Conclusion: Further studies with larger populations and shorter duration of illness are needed to clarify the question of the possible efficacy of vitamin B 6 in treatment of psychotic symptoms in schizophrenia.