BACKGROUND: Elevated Minnesota Multiphasic Personality Inventory (MMPI) scores on the hysteria (Hy) scale are reported in several forms of pain. Previous results were possibly biased by diagnostic heterogeneity (psychogenic, somatic and mixed pain syndromes included in the same index sample) or Hy heterogeneity (failure to differentiate Hy scores into clinically meaningful sub-scales, such as admission of symptoms [Ad] and denial of symptoms [Dn]).