Tuesday, February 22, 2011

The Placebo Effect

We talked about placebos for a little while in the "Psychology of Consciousness" class I'm taking this semester. So far, it's been mostly the various theories that encompass the history of the study of consciousness, but is still sometimes a little too abstract for me. That said, the placebo effect is pretty real and pretty fascinating.

There seems to be a physiological basis for the placebo effect in pain - some neurons of the Raphe nuclei in the brainstem project down to the dorsal horn of the spinal cord, where primary sensory neurons enter on their way up from the body. Those involved in sensing pain make a synapse here, and that's where this effect can act. The Raphe neurons release serotonin to stimulate inhibitory interneurons, which then release enkephalin (an endogenous opioid) directly onto the axons of the pain-sensing neurons before they transmit the signal to the secondary neurons in the pain pathway. So less pain.

But this still doesn't answer the question of how our beliefs can affect the size of the effect, and why that effect is always about half of whatever we believe it should be. And then there's the placebos that are used for things other than just pain (homeopathy, for instance). Do they in fact work better than no treatment at all? And if they do, how? So many questions, so little known.

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