Belief and the Brain

Recently we had a discussion here about alternative
medicine, and we talked a little about the placebo effect.

Today I ran across an article reviewing some research on
 the placebo effect, I will summarize it below. The gist
of these studies is that positive expectations, and a
belief that something will work actually makes it work,
and causes measurable changes in brain chemistry.

It has been documented in prior research that the placebo
effect is probably mediated by endogenous opiates, because
this effect is blocked by naloxone, which is an opiod
antagonist.

So a recent study decided to study the endogenous opiate
system placebo effect by using PET scans.

In this study published in September in the Journal of
Neuroscience researchers using PET scans were able to
document a link between anticipation of treatment and
activity of the mu-opiod receptors that correlated with a
placebo effect. In this study volunteers were subjected
to muscle pain by injection of hypertonic saline. The
subjects had been told that the study was to measure the
effects of a new pain medication, and were told that they
would get either the medication or placebo. In fact all
subjects received placebo. Some subjects thought that
they received the medication and in these subjects, there
was increased activity in mu-opiod receptor activity
mainly in pre-frontal cortex areas. This increased
activity was associated with lower pain ratings.

Other neurotransmitters are also affected by the placebo
effect. Previous research has shown increased dopamine
levels in patients with Parkinsons Disease that were given
a placebo. In fact the dopamine levels in patients given
a placebo injection were comparable to levels in patients
given an active drug. Similarly a study published in
2004 compared Parkinsons patients that had embryonic stem
cell implants to patients that had sham surgery, and those
that had the actual implants overall were doing no better
than those that had the actual implants. However, those
patients that thought they had the actual surgery had
better quality of life and actual health regardless of
what treatment they received.

Also from 2004 a study on the effects of an antidepressant
were measured. Prior to the study the patients were asked
what they expected from the drug, and were told to choose
from three alternatives that summed up their expectation
of the effect of the medicine: “not at all effectve”,
“somewhat effective” or “very effective.” All patients
were given the medication, but those whose anticipation
was “very effective” had a 90% positive response compared
to 30% of those that expected a less effective response.

  
Received on Thu Jan 12 12:38:24 2006