Table 1.

Classification of offspring risk groups: Seven-group and five-group models

Seven-group basic model	Father and cotwin's diagnostic status	G	E	n	Risk type
Group
HGHE-D	DD or DD/AD	High	High	455	Father's DD risk
HGLE-D	Father unaffected, MZ cotwin DD or DD/AD	High	Low	75	MZ cotwin's DD risk
MGLE-D	Father unaffected, DZ cotwin DD or DD/AD	Moderate	Low	81	DZ cotwin's DD risk
HGHE-A	AD (without DD)	High	High	548	Father's AD risk
HGLE-A	Father unaffected, MZ cotwin AD (without DD)	High	Low	170	MZ cotwin's AD risk
MGLE-A	Father unaffected, DZ cotwin AD (without DD)	Moderate	Low	148	DZ cotwin's AD risk
LGLE	None	Low	Low	440	None

Five-group model combining Groups 2 and 5 and 3 and 6	Dx	G	E	n	Risk type
Group
HGHE-D	DD or DD/AD	High	High	455	Father's DD risk
HGHE-A	AD without DD	High	High	548	Father's AD risk
HGHE	Father unaffected, MZ cotwin in DD or AD or both	High	Low	245	MZ cotwin's DD or AD risk
MGLE	Father unaffected, DZ cotwin DD or AD or both	Moderate	Low	229	DZ cotwin's DD or AD risk
LGLE	None	Low	Low	440	None

Notes: G = genetic; E = environmental; n = number of offspring; HG = high genetic; HE = high environmental; D = drug; DD = drug dependence; AD = alcohol dependence; LE = low environmental; MZ = monozygotic; MG = medium genetic; DZ = dizygotic; A = alcohol; LG = low genetic; Dx = diagnosis.