Table 2.

Means and standard deviations for Emotional Instability and Extraversion by fatigue<break/>definition and zygosity

	Chronic fatigue of 6 months or longer		CFS-like illness
	Cases MZ n = 214 DZ n = 94	Controls MZ n = 99 DZ n = 51	Cases MZ n = 148 DZ n = 66	Controls MZ n = 133 DZ n = 65
Emotional Instability
MZ Twins, mean (SD)	56 (11)	56 (11)	55 (11)	56 (11)
DZ Twins, mean (SD)	58 (11)	52 (10)	59 (10)	53 (10)
Extraversion
MZ Twins, mean (SD)	44 (13)	49 (10)	43 (13)	49 (11)
DZ Twins, mean (SD)	44 (11)	52 (9)	44 (11)	51 (9)

CFS = chronic fatigue syndrome; MZ = monozygotic; DZ = dizygotic; SD = standard deviation