COLLEGE STATION, June 12 - Human emotion can be a powerful force, fueling everything from improbable sports championships to tragic acts of violence. Now there's evidence showing how powerful human emotional states can be when it comes to determining a person's ability to feel pain.
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."
Meagher believes previous conflicting reports of the effects of anxiety on human pain were due to a failure to properly distinguish between the emotional states of fear and anxiety.
Fear, Meagher explains, is an immediate alarm reaction to present threat, characterized by feelings to escape and accompanied by specific physiological changes. Anxiety, on the other hand, is a future-oriented emotion characterized by anticipation of potential threats.
Fear mobilizes a person to take action - the commonly known "fight or flight" response - but anxiety leads to scanning of the environment and body, resulting in increased sensory input, she says.
With these distinctions in mind, the conclusions make sense from an evolutionary point of view, Meagher notes.
Confronted with life-threatening situations, which would elicit fear, the body reacts by shutting off the pain response because feeling pain might get in the way of survival, she says. "Alternatively, during times of low threat - those times likely to produce a state of anxiety rather than fear - the chance of survival is increased if pain is enhanced so that behavioral responses can occur to minimize tissue damage," Meagher explains.
Meagher's work also shows that positive emotions can lead to pain reduction as long as a minimal level of arousal is reached, but negative emotions only lead to pain reduction when they are highly arousing. In fact, she says, negative emotions can actually facilitate pain if they are only low to moderately arousing.