The Danish PET/depression project: PET findings in patients with major depression

Background. It is hypothesized from previous positron emission tomography ( PET) studies of patients with major depression that dysfunction of regions of the limbic, system and the frontal lobes in close connection with the ba sal ganglia is involved in the pathophysiology of major depression. Methods. By means of PET and O-15 labelled radioactive water we determined an index of the neuronal activity by mapping the cerebral blood flow distri bution of 42 unselected in-patients suffering from moderate to severe depre ssion and 47 healthy controls controlling for age and gender. The PET maps were co-registered to magnetic resonance images of the anatomy of the brain . Results. The functions-of-interest analysis revealed significant gender dif ferences in cerebral blood flow and changes in the relative distribution of the blood with increasing age. The patients had increased activity of the hippocampus and the cerebellum compared to the healthy controls when correc ted for these confounders and the influence of antidepressant medication. F urthermore, data in the Danish Psychiatric Central Register showed that the patients studied were representative of the population of depressed patien ts admitted to the hospital during the study period. Conclusion. Our main finding is increased blood flow to the hippocampus, ev en when controlling for a number of confounders. This is in accordance with a rapidly expanding literature suggesting an important role for this struc ture in major depression.