NEUROPSYCHIATRIC DISORDERS ASSOCIATED WITH NUTRITIONAL DEFICIENCIES - INCIDENCE AND THERAPEUTIC IMPLICATIONS

Deficiencies of various vitamins are associated with a variety of neuropsychiatric manifestations. Depression is a feature of deficiencies of folic acid, vitamin B-2 (riboflavin) and vitamin B-6 (pyridoxine), while vitamin B-1 (thiamine) deficiency is associated with several psychosyndromes including alcoholism and schizophrenia. Data from recent studies of vitamin deficiency reveal that gross manifestations such as beri-beri (characteristics include Wernicke's encephalopathy and Korsakoff's syndrome) and pellagra (characteristics include fatigue, insomnia and encephalopathy) are now relatively rare in the Western world. However, milder and subclinical syndromes are still common. For example, the prevalence of low levels of vitamin B-12 (cyanocobalamin) is has been estimated to be 5.8 to 26.1% in psychiatric patients, while that of folic acid is higher at 15 to 51% (derived from various studies). Despite these apparent associations, whether deficiencies of vitamins are causal in neuropsychiatric disorders or a result of them is difficult to determine. For example, there is little direct evidence of a causal role for folic acid in neuropsychiatric disorders, except in the rare in-born errors of metabolism that present with neuropsychiatric abnormalities. It is known that folic acid deficiency is associated with the use of many therapeutic drugs, concomitant physical illnesses and chronicity of psychiatric illness. However, retrospective studies of the effects of folic acid replacement therapy in deficient patients, employing clinical and social outcome criteria, have shown an improvement in psychiatric symptoms over a period of 6 to 12 months in most patients. Controlled studies of folic acid replacement therapy are also encouraging. In 1 double-blind, placebo-controlled, add-on trial involving patients with endogenous depression and schizophrenia, the majority of folic acid-treated patients improved compared with placebo recipients. The situation with regard to a causal role for other vitamins in neuropsychiatric disorders is even less clear. Obviously, more data are needed in this area to assist clinicians in determining the aetiology of episodes of depression and other neuropsychiatric disorders and, ultimately, their treatment.