1. Sixty-two patients were studied in whom organic disease of the central nervous system was probably induced, at least in part, by metabolic deficiency. Mental symptoms were present in 25 of these cases.2. The deficiency is termed a "neurometabolic crisis." It may be caused by absolute or relative avitaminosis, by starvation of various origins or by endocrine factors.3. Causation of the mental symptoms in certain cases is outlined, schematically, as a complex system of vicious circles, in which the two factors of anxiety and metabolic imbalance both play a part.4. In view of our personal good results in such cases, a high-vitamin diet is recommended for tentative trial not only in acute or subacute psychoses characterized by delirium and amentia, but also in acute episodes of the organic-reaction type which occur in the course of schizophrenic and manic-depressive psychosis.