This is kind of an old study but I came across it again in organizing my files and found the online description here.
Texas A&M University psychologist Mary W. Meagher, who has conducted pain research for 16 years, says two emotional states - fear and anxiety - have profoundly different effects on a person's ability to feel pain.
"Fear and anxiety have divergent effects on pain reactivity in humans: fear reduces pain, whereas anxiety has a sensitizing, or enhancing effect," says Meagher, who holds joint appointments in clinical psychology and behavioral neuroscience.
Her conclusions are based on her and graduate student Jamie L. Rhudy's recent work focusing on the role of human emotion on pain. Previous animal studies have suggested that fear inhibits pain and anxiety enhances it, but Meagher's results support the view that emotional states influence human pain reactivity.
"From a clinical perspective, these data suggest that a patient anticipating an unpredictable threatening event will experience enhanced pain," she says. "In contrast, a patient that has been exposed to a threatening event will experience a fear state that inhibits pain processing."