A re-evaluation of glucose tolerance in schizophrenia

Abstract

MANY different biochemical and physiological abnormalities have been reported in schizophrenia. Carbohydrate metabolism is one area in which abnormalities have been reported since 1919.1,2 Both diagnostic and methodological problems are apparent f rom the literature. Many reports give no explicit diagnostic criteria s--2~ and it would appear that abnormalities are not specific for schizophrenia. Similar abnormalities have been reported in manic depressive psychosis, 18,18,x0,21,22,~0-28 involutional psychosis,m, ss randomly selected psychiatric patients,10,19, $9,s0 neurosis and psyehopathy ~,~,ls and in senile psychosis and reactive conditions: 7,s2 In the studies on schizophrenic patients few investigators controlled diet,4,s, 9 weightZO,al, ss physical status 81,32 and medication, 11,13,zo,19,31,s2 and of those involving matched control groups 7,10,11,14,19,21,31,32 few matched diets. 21,31,zs In some cascs thc abnormality is quite variableS, 7,9 and in one ss the abnormality reported is the reverse of the abnormality reported in other studies. 13,~,s2,~ The recent development of techniques for continuously monitoring venous glucose has provided an extremely useful tool for a re-examination of carbohydrate metabolism. As the data obtained arc more complete, mathematical analysis can bc employed to give a more accurate description and allow the delineation of subtle differences between curves. In the event that differences between schizophrcnics and non-schizophrenics cannot bc found with the use of sensitive measures of glucose tolerance in studies with rigorously controlled conditions it would bc extremely doubtful that any relationship exists between schizophrenia and glucose tolerance. Our hypothesis was that a difference would be shown between controls and schizophrenic patients when both were on an adequate diet. In previous studies, 4,~,8s a relationship between diet and glucose tolerance was demonstrated.