Racial Differences in Pain Perception: a Biological Basis

Abstract

Behavioral differences between the various human races have been observed (e.g. intelligence). The perception of pain is essential for human survival. Individual as well as group differences have been reported in pain behavior, suggesting that pain behavior may be genetically influenced. To develop more efficacious pain treatment, it will be important to understand the genetic mechanism of pain and to uncover any differences between the races. The presence of genetic differences will indicate the need to consider race in future pain management strategies. Key Words: nociception; pain; racial differences Racial differences in skeleto-muscular, endocrine and nervous systems have been previously described (e.g., Baker, 1974; Yanovski et al., 1996). Because phenotype and behavior shows significant heritability, they are, at least partially, genetically mediated. For example, Asian American students will academically outperform black American students, regardless of socio-economic standing (NSF, 1994). Conversely, it should be no surprise that blacks are athletically more able than Asians. Genes are thought to mediate many behaviors, ranging from aggression to self-discipline, since their level of expression markedly differ between the races and have moderate to high heritabilities (Rushton, 1995). The perception of pain is a mechanism by which humans receive bodily as well as environmental information. Although it may seem that having no pain perception maybe beneficial, in reality a dysfunctional pain perception system is deleterious. For example, patients who are congenitally insensitive to pain repeatedly inflict severe injuries upon themselves and require constant medical attention. The reduced pain perception is due to gene mutations that alter normal sensory neuron function (Mardy et al., 1999). Conversely, heritable pathologies exist that exacerbate pain perception, such that the usual stimulus is now perceived as extremely painful (references in Mogil et al., 1999a). Growing evidence indicate that genes play an important role in pain perception, just as genes may be important in other kinds of behaviors. The current paper reviews racial differences in pain perception. Evidence for the genetic basis of pain perception is reviewed in animal studies, which may have relevance to humans. Ultimately, the goal is to identify genes that are involved in normal as well as abnormal pain sensation and to devise treatment based on empirical data. Pain is defined as the sensation that accompanies impending or ongoing tissue damage. Pain detection and the response to it is crucial for survival. The diverse responses to pain range from simple to complex behaviors, from a withdrawal reflex to remembering that touching a hot stove has dire consequences. In humans, the painful sensory experience has been characterized as biphasic, the first phase being perceptual/sensory and the second phase being reactive (Bonica, 1990). This means that a pain experience can be compartmentalized into a phase where pain is detected or realized, then a phase where there is a response to pain. The response to pain integrates emotion, affect and memory. There are those who argue that environment shapes pain behavior. Environmentalists argue that individual as well as racial differences in pain perception are due to cultural background. Another force that shapes pain behavior is learning (Melzack and Wall, 1982). Pain - Nurture? Pain has a unique status in human societies. Ceremonial torture and mutilation, involving excruciating pain, are used by some societies as tests of loyalty or worthiness. Thus, high tolerance of pain, in a religious or spiritual context, is viewed as desirable. However, long-term pain arising from illness, is viewed differently. Rural Black Africans believe that illness and the accompanying pain are signs of possession by evil spirits and an inevitable facts of life. …