Table 1.

Demographic characteristics

Category	Subcategories	N (pairs)
		MZ	DZ
Zygosity	Total	81	33
Gender	Women	52	12
	Men	29	8
	Mixed	-	13
Age	18–30	40	21
	31–40	13	3
	41–50	9	3
	51–60	13	2
	61–70	6	4
Race	African American	3	2
	American Indian	1	1
	Asian	12	5
	Caucasian	64	25
	Pacific Islander	1	0
Ethnicity	Hispanic	14	6
	Non-Hispanic	67	27

DZ = dizygotic, MZ = monozygotic, N = number

This table has been reproduced with permission of the International Association for the Study of Pain_® (IASP_®). The table may not be reproduced for any other purpose without permission.