1. Home>
2. Specialties>
3. Psychiatry>
4. Summary and Comment

How Placebo Affects the Depressed Brain

In a study of 51 depressed patients, EEGs showed that placebo responders and antidepressant responders have distinctly different brain mechanisms.

Placebos are often therapeutically effective in patients with depression; as much as 50% to 75% of the therapeutic effects of antidepressant medications have been attributed to the placebo effect. To examine the biologic mechanism of placebos, researchers used quantitative electroencephalography (QEEG) to study brain function in 51 depressed patients who participated in 2 double-blind, placebo-controlled studies involving 8-weeks' treatment with fluoxetine or venlafaxine. QEEG measures of power have been shown to correlate with antidepressant response. By using a 35-electrode EEG montage and an algorithm to calculate relative power among all brain sites, investigators also computed "cordance," which reflects cerebral perfusion.

Patients included medication responders, medication nonresponders, placebo responders, and placebo nonresponders. By 2 weeks, the medication-responder group (52% of medication recipients) showed slight decreases in prefrontal cordance from baseline values. The placebo-responder group (38% of placebo recipients) showed significant increases in prefrontal cordance, compared with both baseline values and with values of medication responders. Nonresponders to medication or placebo showed no significant changes in cordance. Placebo and medication responders did not differ on clinical characteristics. QEEG power was unchanged in all groups.

Comment: These findings suggest that the brain mechanism in depressed patients that leads to clinical improvement with placebo is distinctly different from the mechanism that leads to clinical improvement with antidepressants. The inexpensive methods of determining brain function in this study may prove useful for estimation of cerebral perfusion in other studies and for early identification of medication and placebo responders.

— Joel Yager, MD

Published in Journal Watch Psychiatry February 6, 2002

Citation(s):

Leuchter AF et al. Changes in brain function of depressed subjects during treatment with placebo. Am J Psychiatry 2002 Jan; 159:122-9.

• Original article (Subscription may be required)
• Medline abstract (Free)