Over at Clinical Psychology and Psychiatry, an article regarding the long-term effects of placebos is reviewed.
Here's a little more information about those little, inactive pills used in research (1). In a 2002 study, Leuchter and colleagues studied the EEG's (electroencephalographs) of depressed patients who received antidepressant therapy(either fluoxetine or venlafaxine) or placebo treatment. The researchers analyzed the data of responders, "Overall, 52% of the subjects (13 of 25) receiving antidepressant medication responded to treatment, and 38% of those receiving placebo (10 of 26) responded. Medication responders and placebo responders could not be distinguished on the basis of their initial or final level of depression."
Typical right? That's because the researchers performed a placebo washout (common practice in drug clinical trials)."After enrollment, all subjects received single-blind, placebo lead-in treatment for 1 week; subjects who met response criteria (Hamilton depression scale score ≤10) after this week were removed from the study." Would research results be different if this practice was not done? It hasn't been studied as far as I know.
When the EEG's of the antidepressant treated were examine, "At week 2, the medication responder subjects showed a unique and significant decrease in prefrontal cordance that differentiated them from the three other groups." The placebo group, "showed slight increases in prefrontal cordance...at week 4, this increase achieved significance in the placebo responders, who differed both from their group baseline and from the medication responders."
So antidepressants decreased frontal activity of depressed patients while placebo increased frontal activity of depressed patients. Pretty amazing for a supposedly inactive substance. I wonder what was occurring in the brains of those who were washed out for responding to placebo in the first week? I guess we'll never know.