Hawk, I do understand your question, and yes, opioids have been implicated in sensitizing the nervous system to pain.
Your question is valid, and perhaps deserves some research, but I don't see how if PSWT and opioids are antagonists that would explain the results.
Are you hypothesizing that PSWT might block the effectiveness of opioids? If it is the other way around, with opioids blocking the effects of PSWT, then both groups should just be equal.
Given that the variability is so high, it is possible, that is what is happening. Either way, not the result everyone was hoping for. Which is often the way science works.
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