Endogenous Opioids and Chronic Pain Intensity
Bibliographic record
Abstract
OBJECTIVE: To test whether endogenous opioid antinociceptive system dysfunction evidenced in response to acute pain stimuli is associated with increased clinical pain intensity in chronic pain sufferers, and to determine whether this association is moderated by disability level. DESIGN: A double-blind, placebo-controlled, randomized crossover design. Subjects underwent laboratory acute finger pressure pain stimulation and ischemic pain stimulation under placebo and under opioid blockade with naloxone. The primary independent measures, reflecting degree of endogenous opioid antinociception, were opioid Blockade Effects derived to reflect the change elicited by naloxone in pain intensity ratings for the acute pain tasks. High and Low Disability groups were derived based on Pain Disability Index scores to allow examination of the influence of disability level on the relationship between Blockade Effects and chronic pain intensity. SUBJECTS: Twenty-eight chronic low back pain sufferers. OUTCOME MEASURE: Seven-day diary ratings of overall chronic pain intensity based on McGill Pain Questionnaire-Short Form total scores. RESULTS: Greater daily chronic pain intensity was associated with greater placebo acute pain sensitivity in the laboratory (P < 0.05). Positive Blockade Effects (ie, presence of opioid analgesia) were associated as expected with lower placebo-condition acute pain sensitivity in the laboratory (P < 0.05). In main effects analyses, Blockade Effects were not associated significantly with daily chronic pain intensity. This absence of overall main effects was accounted for by significant opposing interactions between disability level and Blockade Effects (P < 0.05). Negative Blockade Effects (ie, absence of endogenous opioid analgesia to acute pain) in the High Disability group were associated with greater daily chronic pain intensity, consistent with the hypothesized effects of chronic pain-related opioid dysfunction. In contrast, Positive Blockade Effects (ie, effective opioid analgesia to acute pain) were associated with higher daily chronic pain intensity in the Low Disability group. CONCLUSIONS: These results suggest that endogenous opioid antinociceptive system dysfunction may contribute to elevated acute and chronic pain sensitivity among more disabled chronic pain patients. Among less disabled patients, chronic pain may serve as a primer producing up-regulated opioid antinociceptive responses to acute pain
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".