Pathophysiological significance of cerebral perfusion abnormalities in major depression-trait or state marker?

Considerable data support the existence of impaired regional cerebral blood flow in major depression. However, it is unclear whether the impairment in brain function in major depression is a "state" marker, reversible upon remission, or an enduring trait phenomenon. We have studied brain technetium-99m hexamethylpropyleneamineoxime (Tc-99m HMPAO) uptake ratios in healthy subjects of various ages, in depressed patients before and after electroconvulsive therapy (ECT) and in healthy subjects before and after administration of fluoxetine. Analysis of our findings, presented along with research data of other groups, strongly suggests that reduced cerebral perfusion in major depression is reversible by successful treatment. Furthermore, since fluoxetine had little effect on cerebral perfusion in healthy subjects, and ECT had little effect on cerebral perfusion in depressed patients who did not respond to treatment, we contend that increases in perfusion represent remission rather than treatment effect. Therefore, reduced perfusion in major depression appears to be a state marker and not a trait abnormality.