The placebo effect: caused by the brain

[Diamond]

http://www.theregister.co.uk/2005/08/24/placebo_natural_high/

A brain imaging study, conducted by researchers at the University of Michigan, has revealed that our bodies' natural painkilling system might play a role in the placebo effect.

The researchers injected saline solution into the jaws of 14 healthy male volunteers. The procedure is harmless, but slightly painful, so all were told to expect painkilling medication. Some of the subjects were given real painkillers, others were given placebos.

All groups recorded their experience of pain every 15 seconds over the course of the 20 minute procedure, while their brains were scanned with the PET (positron emission tomography) machine.

When subjects were told they would receive painkillers, the parts of the brain that produce our bodies' natural painkillers, the mu-opioid receptors, kicked up a storm.

The brain activity was proportional to the expectations the subjects had about how effective the painkillers would be. The researchers say this is the first direct evidence that endorphins can help explain how the placebo effect works.

[athon]

I've always wondered if the placebo effect is related to stress reduction.

In a 'fight or flight' situation, immediate retreat or defence takes precedence over long-term healing. The body's resources are therefore devoted to the systems and procedures that are useful immediately. When stress is reduced, the body can devote these energies to healing.

Placebo effects might be a result of the brain being intentionally 'destressed' by a certain behaviour. Decreased pain and increased healing processes are typical in low stress environments. Obviously, being aware of an injury or an illness is itself a stress. Behaving in a manner that means you believe your state of health will improve might well decrease stress and, in turn, assist in improving recovery.

This is just a speculation, as I've never read an studies that compare forms of stress reduction with placebo trials. It would be interesting, though.

Athon

[stup_id]

Hello, I agree with must that Athon wrote, except for the "decreased pain" in low stress situation... Altough in a relaxed environment pain can be lower than in stressing situations (which i'm not totally convinced of). Just the opposite effect has been proved, the high rush of adrenaline, of course the stress related hormone most well studied; shows that high stress levels can diminish significantly the pain we feel.

This is for instance the explanation about profesional sport players who get bad injured in a game but wouldn't notice after it finishes, or in the war according to chronics of the veterans, that sometimes because of stress they hadn't even noticed they were shot, mistaking the pain for a simple and seemlingly unimportant wound.

Apparently the catecholamines (such as adrenaline) can activate specific neural pathways in the lower parts of the brain (pontum, raquideal bulb...) that prevent or inhibit impulses of pain coming up trough the spinal fibers.

On the contrary, hormones related to "low stress" situations, such as corticosteroids and serotonin, are even directly involved in carrying messages of pain to the cortex.

Woosh.. i hope i'm not mixing up my neurophisiology courses.. haha I welcome any correction about the details but the point still stands... there's a lot of evidence that high stress situation diminishes the sense of pain in the individual...