Table 4. Maximum likelihood estimates of familial correlations.

	r ADHD index	95% CI
MZ twins	0.36	0.31–0.40
MZ Male	0.342	0.244–0.428
MZ Female	0.380	0.324–0.431
Male first-degree relatives	0.09	0.032–0.158
DZ Male	0.145	−0.092–0.374
brother - male twin	0.081	−0.066–0.221
brother - brother	0.035	−0.202–0.267
father -son	0.076	0.075–0.143
Female first-degree relatives	0.19	0.151–0.223
DZ Female	0.212	0.112–0.305
sister - female twin	0.217	0.135–0.290
sister - sister	0.107	−0.105–0.303
mother -daughter	0.191	0.144–0.235
Female-Male first-degree relatives	0.12	0.101–0.156
DZ Opposite Sex	0.112	0.020–0.203
brother - female twin	0.066	−0.049–0.178
sister - brother	0.023	−0.154–0.163
sister – male twin	0.101	0.033–0.216
mother - son	0.122	0.062–0.179
father -daughter	0.139	0.089–0.188
Parents (father – mother)	0.11	0.061–0.164