title: Anger and pain sensitivity in chronic low back pain patients and pain-free controls: the role of endogenous opioids.
abstract: The experience of anger (i.e. trait anger) and anger management style (i.e. anger-in, anger-out) are related to sensitivity to acute and chronic pain stimuli, although underlying mechanisms are unknown. This study tested whether anger variables are associated with impaired endogenous opioid antinociceptive activity, and whether these relationships differed between chronic pain patients and healthy normals. Forty-three chronic low back pain (LBP) sufferers and 45 pain-free normals received opioid blockade (8 mg naloxone i.v.) or placebo blockade (saline) in randomized, counterbalanced order in separate sessions. During each session, subjects participated in a 1-min finger pressure pain task followed by an ischemic forearm pain task (maximum duration 5 min), providing pain intensity ratings during and immediately following each task. As a measure of opioid antinociceptive function, drug effects were derived by subtracting placebo from blockade condition pain ratings. Multivariate general linear model analyses indicated that anger-out, but not anger-in, had significant main effects on both finger pressure drug effects (P < 0.05) and ischemic task drug effects (P < 0.05). As hypothesized, high anger-out scores were associated with an absence of opioid analgesia during the acute pain tasks; low anger-out scores were associated with effective opioid analgesia. A similar non-significant trend was noted for trait anger on finger pressure drug effects (P < 0.06). Anger-out x LBP/normal interactions were non-significant, suggesting that links between anger-out and drug effects were similar for patients and normals. Controlling for depression did not eliminate the significant relationship between anger-out and drug effects. Findings suggest that anger-in and anger-out affect pain sensitivity through different mechanisms: only the effects of anger-out may be mediated by endogenous opioid dysfunction.
authors.affiliation: Department of Anesthesiology, Vanderbilt University School of Medicine, Suite 403-G MAB, 1211 Twenty-First Avenue South, Nashville, TN 37232-1557, USA. stephen.bruehl@mcmail.vanderbuilt.edu
authors.forename: Stephen
authors.initials: S
authors.lastname: Bruehl
authors.forename: John W
authors.initials: JW
authors.lastname: Burns
authors.forename: Ok Yung
authors.initials: OY
authors.lastname: Chung
authors.forename: Pamela
authors.initials: P
authors.lastname: Ward
authors.forename: Benjamin
authors.initials: B
authors.lastname: Johnson
mesh_terms: D000208:Acute Disease; D000786:Anger; D002908:Chronic Disease; D018592:Cross-Over Studies; D003863:Depression / Q000503:physiopathology / Q000523:psychology; D004311:Double-Blind Method; D005385:Fingers; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology* / Q000523:psychology*; D015999:Multivariate Analysis; D009270:Naloxone / Q000008:administration & dosage; D009292:Narcotic Antagonists / Q000008:administration & dosage; D009619:Nociceptors / Q000502:physiology; D018847:Opioid Peptides / Q000502:physiology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology* / Q000523:psychology; D010919:Placebos; D011312:Pressure
chemical_list: D009292:Narcotic Antagonists; D018847:Opioid Peptides; D010919:Placebos; D009270:Naloxone