Pharmacokinetics of antidepressants: why and how they are relevant to treatment.

Findings from computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT) studies of patients with depression suggest that this mood disorder is associated with regional brain dysfunction. The various elements of depression--dysphoria, anhedonia, helplessness, and sad affect--are all closely associated with changes in cerebral blood flow and/or metabolism in the frontal-temporal cortex and caudate nucleus. A compelling convergence of information from psychiatric and neurologic investigations indicates that depression is mediated by a restricted set of brain structures.