Table 1.
Sibling Correlations of Nine Autism Endophenotypes Tested for Familiality
| Endophenotype | ADI-RItem | No. ofSib Pairs | Correlation | Pa |
| Age at first word | A12 | 113 | .32 | .0006 |
| Age at first phrase | A13 | 76 | .26 | .021 |
| Difference between ages at first word and phrase | 74 | .23 | .05 | |
| Language level | A19 | 155 | .03 | NS |
| Repetitive and stereotyped behavior | DD total | 108 | .25 | .01 |
| Circumscribed interests | A70a | 121 | .23 | .001 |
| Unusual preoccupations | A71a | 154 | .14 | NS |
| Repetitive use of objects | A72a | 143 | .02 | NS |
| Difficulties with changes in routines or environment | A73a | 155 | .28 | .0001 |
a
NS = not significant.