A Biochemical Approach to Depressive Illness

We also have a fourth possibility, namely that the changes in metabolism may be taking place only in the brain although the same metabolic process is to be found also in other tissues. If this situation exists it may be impossible to infer changes in cerebral tissue from changes in metabolites in blood and urine. Studies of cerebral metabolism in depressive illness are necessary in each of the above situations. In 1, 2 and 3 above they are necessary to justify the assumptions relating general and cerebral metabolism, whilst in case 4 the information is not obtainable by any other technique.