Effects of medications on cerebral blood flow in late-life depression.

Both normal aging and late-life depression (LLD) are associated with reductions in regional cerebral blood flow (rCBF). The impact of medication treatment in baseline rCBF abnormalities in LLD is being investigated via functional imaging research. Some of this work can be informed by pharmacologic challenge studies, which exploit the role of serotonin in regulating rCBF. Preliminary evidence suggests that there may be both state- and trait-level disturbances in rCBF in LLD, and that a common pathway towards clinical response to somatic antidepressant treatments involves reduction in rCBF in critical prefrontal cortical brain regions. Studies of the effects of medications on rCBF in LLD have implications for understanding the neurobiology of treatment resistance in the elderly as well as the mechanisms of action of antidepressant treatments.