Glucose metabolism in psychiatric disorders: how can we facilitate comparisons among studies?

Positron emission tomography (PET) offers a possibility to study brain function and its relationship to psychiatric disorders. Clinical studies have demonstrated that several psychiatric diseases are coupled with changes in brain glucose metabolism. Schizophrenia seems to involve a lower metabolism in wide areas of the brain--both cortical and subcortical structures. Depression probably involves dysfunction of the metabolism in dorsolateral prefrontal cortex. Obsessive compulsive disorder, panic disorder, anorexia nervosa and the experience of anxiety may involve increased metabolic rates. The results from the different studies do not allow quantitative comparisons or detailed analyses because of large differences in experimental and clinical methodology. The term Good Clinical PET Practice (GCPP) is suggested to encourage standardization in clinical investigations. GCPP includes standardization of both experimental factors (lumped constant, arterialization, purity of tracer, regions of interest, relative rates) and clinical factors (state of the subject, wakefulness, anxiety, gender, course of the disease) in PET performance.