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Placebo effects are not the “power of positive thinking”

natasa778

Senior Member
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1,774

links to another potentially interesting one - full text available if anyone has the time ...

These findings show that cognitive factors and conditioning are balanced in different ways in placebo analgesia, and this balance is crucial for the activation of opioid or nonopioid systems. Expectation triggers endogenous opioids, whereas conditioning activates specific subsystems. In fact, if conditioning is performed with opioids, placebo analgesia is mediated via opioid receptors, if conditioning is performed with nonopioid drugs, other nonopioid mechanisms result to be involved.
 

Snow Leopard

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These findings show that cognitive factors and conditioning are balanced in different ways in placebo analgesia, and this balance is crucial for the activation of opioid or nonopioid systems. Expectation triggers endogenous opioids, whereas conditioning activates specific subsystems. In fact, if conditioning is performed with opioids, placebo analgesia is mediated via opioid receptors, if conditioning is performed with nonopioid drugs, other nonopioid mechanisms result to be involved.

I would be really really really surprised if this turned out to be true, this is a truly novel claim.

The alternative (and simpler) explanation is what I have been proposing. (that their observations are due to other biases).
 
Last edited:

natasa778

Senior Member
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1,774
I would be really really really surprised if this turned out to be true, this is a truly novel claim.

The alternative (and simpler) explanation is what I have been proposing. (that their observations are due to other biases).

Just started reading it, and it seems well controlled and measured (no self-reports). The experimenters were blinded, as far as I can see, and some of the injections were hidden ...

Btw here is another one on naltrexone blocking the effects of placebo


and another one, with similar findings it seems, as well as a review:

This systematic review assesses six experimental studies into the mechanism of placebo analgesia in human subjects suffering from clinical pain or experimentally induced ischaemic arm pain. Due to their sophisticated designs, these studies probably provide the best evidence that placebo analgesia exists. They also indicate that placebo analgesia is mediated by endogenous opiates. However, there seems to be room for additional studies.

unfortunately all of these are behind a thick paywall


btw I would expect that placebo effects, if real in a biological sense, are totally different - not only in terms of mechanics but to the point of whether they exist at all or not - in different areas such as various types of pain/analgesia, chronic conditions or cancer etc.
 
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Yeah but the 'correlation does not equate to causation' mantra gets a bit silly and extreme too.

Clear thinking is important. I had wondered too if the 'saline solution' did contain some poisons which is rife in the placebos.

But whilst the article discusses the book Mind Over Medicine, I think the Doctor who wrote that maybe suppying the references.

I don't know if the study you quote snowleapord is the one referenced by the Doc.

It would be good to have honest raw data.

Better, to view it direct.

I looked into some of the claims from that book. Dodgy and spun data. Don't trust imo.

It could all be another myth designed on lies.

Lies, incompetence, foolishness, mystical thinking and maybe an occasional bit of truth imo. Very difficult to know.

This SBM article had a number of things relevant to PACE imo.

Hard vs soft measures generally, and also this would seem comparable to the change from bimodal to likert scoring for the Chalder Fatigue Scale:

Even less unexpected is the observation that there was no statistically significant difference in the chances of being pain-free at the 2.5 hour time point between the no-treatment control and the open-label placebo group. This is entirely consistent with what we’ve been arguing here at SBM for a long time, that the more “objective” or “hard” the endpoint (and, although there is still a subjective component, being pain-free is a harder endpoint than stating a pain score), the weaker any placebo effects observed are, to the point that the very “hardest” endpoints, such as tumor regression or survival, are not affected by placebo.

Did anyone sport a reference to the claim that pain free is a 'harder' outcome that reductions on a scale of pain?

Expectation effects are all screwy with PACE, as after they measured patient expectations, they then told those receiving CBT and GET that these treatments had been shown to be effective.

I often wish SBM posts were more thoroughly referenced so that I could steal their references!
 

Snow Leopard

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@natasa778Those studies used Naloxone (not Naltrexone): http://en.wikipedia.org/wiki/Naloxone
I'm guessing that is what you meant to say.

It does a number of interesting things, not limited to opioid receptor binding.

What has been shown is that Naloxone can increase pain sensitivity where the opioid system is involved with blocking pain.

What has not been shown is that the placebo effect in these studies is mediated by a substantial upregulation of endogenous endorphins (compared to no treatment) and that this effect is therefore blocked by blocking these endorphins (with Naloxone).

There was in fact a study that tested this with a control group:
http://www.psychosomaticmedicine.org/content/65/5/786.short
CONCLUSIONS: A placebo response, ie, a reduced pain level, was seen in the Placebo group at 15 minutes after the injection. The placebo response was not related to stress or to beta-endorphin. Expectation of a pain increase in the Nocebo group led to an increase in cortisol, but the expectation of pain increase and the resultant cortisol increase had no effect on pain.

Another interesting study that noted the effect of the social context on the measured placebo effect:
http://www.ncbi.nlm.nih.gov/pubmed/16813849

The placebo effect (on pain) will continue to be an interesting hypothesis (only) so long as the method of action is unknown. I personally wonder why there haven't been more proper controlled studies investigating various levels of endogenous endorphins or other related factors.
But I guess it is much easier just to do a simply pain threshold study, hand out a few questionnaires and be done with it because no one seems to be asking difficult questions anyway. (sound familiar).