Table 1.
Diagnosis of 183 relatives of 183 probands with intellectual disability (ID) by relationship type
| Relatives with psychotic illness
|
Probands with ID
|
Analyses*
P-values
|
|||||
|---|---|---|---|---|---|---|---|
| Relative type | Schizophrenia n (%) | Affective disorder n (%) | Relative type | n | Male | Scenario (1) | Scenario (2) |
| All | 121 (66%) | 62 (34%) | All | 183 | 95 (52%) | <0.00001 | 0.005 |
| First degree | |||||||
| Parent | 49 (64%) | 28 (36%) | Offspring | 77 | 39 (51%) | 0.011 | 0.128 |
| Mother | 39 | 17 | 56 | 29 (52%) | |||
| Father | 10 | 11 | 21 | 10 (48%) | |||
| Sibling | 32 (63%) | 19 (37%) | Sibling | 51 | 27 (53%) | 0.05 | 0.229 |
| Sister | 18 | 11 | 29 | 18 (46%) | |||
| Brother | 14 | 8 | 22 | 9 (41%) | |||
| Offspring | 2 (67%) | 1 (33%) | Parent | 3 | 2 (67%) | – | – |
| Second degree | |||||||
| Aunt/uncle | 30 (68%) | 14 (32%) | Nephew/niece | 44 | 23 (52%) | 0.011 | 0.079 |
| Maternal | 21 | 9 | 30 | 14 (50%) | |||
| Paternal | 9 | 5 | 14 | 9 (56%) | |||
| Niece/nephew | 8 (100%) | 0 | Uncle/aunt | 8 | 4 (50%) | 0.004 | 0.011 |
| Maternal | 4 | 0 | 4 | 4 (100%) | |||
| Paternal | 4 | 0 | 4 | 0 | |||
*
One-tailed binomial tests were used to determine whether there was an excess proportion (P) of ID proband pairs where the relative had schizophrenia. Two possible scenarios were assessed: (1) assuming cumulative incidences of hospitalization for schizophrenia and affective disorder were equal (P = 0.50), and (2) assuming cumulative incidence of hospitalization for schizophrenia was greater than that for affective disorder (P = 0.5658), as recorded for first admission rates in 1943 (Penrose 1991).