Variations in brain gray matter associated with chronic pain.

Variations in brain gray matter volume and density have been reported in association with a variety of disorders characterized by chronic pain, including chronic low back pain, fibromyalgia, and irritable bowel syndrome. Correlation analyses have demonstrated relationships between morphometric and clinical variables. However, conclusions regarding the nature of these relationships are problematic given that currently available data are derived exclusively from cross-sectional studies. Further efforts to determine the relationship between chronic pain and variations in brain morphometry will depend in part on longitudinal studies of patients at various stages of illness, as well as those at risk of the development of chronic pain. Interpretation of findings from morphometric studies also must take into account genetic and experiential factors that recently have been demonstrated to influence brain morphometry and the risk of developing chronic pain.