Regional cerebral blood flow in affective disorder

The results of two-dimensional cerebral blood flow (CBF) studies in depression and the results of measurements of regional CBF (rCBF) using single photon emission computerized tomography (SPECT) are briefly reviewed. A technical outline of both types of method is described. The majority of SPECT studies point to a decreased CBF in untreated patients with a tendency towards normalization, but other studies suggest that, following treatment, there is an increase above normal either from a decreased or an abnormally high initial level. One study has pointed to unipolar patients having lower flow in the right temporal and parietal lobes relative to normals, whereas non-endogenous patients did not differ significantly from normal controls. Bipolar depressives have been found to have higher flow values than normals in the parietal and temporal lobes in the left hemispheres. This relevant aspect or a possible relationship between type of depression and hemispheric asymmetry needs further study for full classification. Thus, most investigations designed to determine which brain structures might be involved in regulating affect have not been very successful, which may be a consequence of the biological heterogeneity of these disorders or of the limited spatial resolution of the techniques used for investigation. Even if some of these technical difficulties can be overcome with measurements of receptor kinetics supplemented, other biological variables that have proved valuable in psychiatry (such as rapid eye movement latency and biogenic amines) should be studied to find more precise biological markers for depressive illness.