MedicalResearch.com Interview with:
Vanda Faria PhD
Department of Psychology
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: It has been debated whether selective serotonin reuptake inhibitors (SSRIs), which are commonly prescribed for depression and anxiety, are more effective than placebo. Concerns have been raised that the beneficial effects of SSRIs, as measured in double-blind clinical trials, may be explained by expectancies (a crucial placebo mechanism) rather than the biochemical compound. But no study has tested experimentally the extent to which the SSRI treatment effect can be influenced by expectancies induced by verbal suggestions.
We compared the efficacy of overt vs. covert administration of an SSRI (escitalopram) in patients with social anxiety disorder. Rather than comparing the SSRI with placebo, we compared it with itself while manipulating the patients’ expectations of improvement. This was achieved by informing one group correctly about the SSRI and its effectiveness (overt group) whereas the comparison (covert) group received incorrect information. By use of a cover story, the covert group was led to believe they were treated with a so called “active placebo”, an ineffective neurokinin-1 antagonist yielding similar side effects as the SSRI but lacking anxiety-reducing properties. But the treatment, dosage and duration was in fact identical in both groups.
Results showed that overt outperformed covert SSRI treatment, as the number of treatment responders was more than three times higher on the main clinical outcome measure when correct information was given. Using neuroimaging (fMRI) we also noted differences between the overt and covert SSRI groups on objective brain activity measures. There were differences between the groups e.g. with regard to activation of the posterior cingulate cortex with treatment, and the functional coupling between this region and the amygdala which is a brain region crucially involved in fear and anxiety. The fMRI results may reflect the interaction between cognition and emotion as the brain changes differently with treatment pending on the expectations of improvement.