It
is well known that the clinical placebo response
is important in depression and is very often
similar to that observed with an antidepressant
drug. A brain imaging study has recently
investigated alterations occuring in the brain
following placebo treatment.
Positron emission tomography (PET) was used to
measure brain glucose metabolism in hospitalized
men with unipolar depression enrolled in
double-blind trial with placebo or fluoxetine.
The effect of the administration of placebo or
fluoxetine was evaluated after 6-week of
treatment.
In placebo responders metabolic increases were
observed in the prefrontal, anterior cingulate,
premotor, parietal, posterior insula, and
posterior cingulate, while decreases were found
in the subgenual cingulate, parahippocampus, and
thalamus. This pattern of brain changes was
similar in responders to fluoxetine. In these
patients, however, subcortical and limbic
alterations were also noted in the brainstem,
striatum, anterior insula, and hippocampus.
The similar increases of cortical and decreases
of limbic-paralimbic glucose metabolism in
placebo and fluoxetine responders suggests that
these changes may be necessary for the remission
of depression. However it would appear that the
benefit found in the clinical response after
long-term treatment and the relapse prevention
found in the fluoxetine responders may be linked
to the additional metabolic alterations
localised in the subcortical and limbic
regions. Am
J Psychiatry 159: 728-737, 2002