Reduce stress. Reduce pain?

 Might reducing negative emotions explain placebo-associated pain reduction?

And, should the stress response be included in every placebo-controlled study?

First, the details.

• 63 students were tested on 2 separate days.
• One day they took capsules containing lactose, but were told the capsules contained a potent painkiller.
• The next time, they were told the same thing, but no capsules were taken.
• The volunteers didn’t know the treatment given — single-blinded.
• Pain was induced by placing a thermal probe (+46°C, 115°F) on the forearm for 240 seconds.
• Electrocardiogram (ECG) was used to measure heart rate variability.
• Subjective measurements included pain intensity, pain unpleasantness, stress, arousal, and mood.

And, the results.

• There was a placebo effect on pain intensity that was accompanied by a reduction in subjective stress and heart activity.
• These were the only factors independently associated with pain intensity.
• Reduced subjective stress was the only predictor for the placebo analgesic response.

The bottom line?
The authors concluded, “Reduced negative emotional activation could be a mechanism in placebo analgesia.”

My take is that every placebo-controlled study should include ECG monitoring in order to account for any response that might be associated with stress-reduction.

10/3/08 20:15 JR