. Author manuscript; available in PMC: 2013 Nov 15.

Published in final edited form as: Gastroenterology. 2010 Feb 19;138(4):10.1053/j.gastro.2010.02.037. doi: 10.1053/j.gastro.2010.02.037

Table 2.

Twin Studies of IBS

	No. of twin pairs	Case definition	Data collection method	Genetic liability (%)	Heritability in best-fit model (%)
	No. of twin pairs	Case definition	Data collection method	Genetic liability (%)	Additive genetic	Shared environment	Individual environment
Australian Twin Study	343	Functional bowel disease	No. of symptoms reported by interview	20	57	0	43
Virginia Twin Study	6060	IBS	Check box by IBS	8.8	—	—	—
Minnesota Twin Study	986	IBS by Rome II	Validated bowel disease questionnaire	16	22	0	78
Norwegian Twin Study	3334	IBS	Check box by IBS	13.3	48	0	52
British Twin Study	1870	IBS by Rome II	Validated questionnaire	1	0	26	74