Table 1.

Distribution of educational level and alcohol problems in twin individuals across zygosity and sex

Variable	MZF (n = 920)	DZF (n = 1,732)	MZM (n = 626)	DZM (n = 1,580)	Total (n = 4,858)
Education, M (SD)	13.6(2.4)	13.3 (2.6)	13.0 (2.3)	12.8(2.3)	13.2 (2.5)
RAPI, M (SD)	4.6 (6.2)	4.5 (6.1)	6.7 (8.1)	7.6 (8.0)	5.8 (7.2)
Max. drinks, M (SD)	11.6(6.2)	11.9(6.2)	21.1 (10.2)	21.8(9.8)	16.2 (9.4)

Notes: Dizygotic female (DZF) and dizygotic male (DZM) individuals in the table are drawn from both same-sex and opposite-sex DZ pairs. MZF = monozygotic females; MZM = monozygotic males; RAPI = Rutgers Alcohol Problem Index; max. drinks = maximum number of drinks consumed in a 24−hour period.