Mean level (SD) | Range | p value | ||
All patients | 3.4 (1.1) | 1–6 | ||
Their siblings | n = 85 pairs | 4.5 (1.1) | 3–6 | p < 0.0001 |
Male patients | 3.4 (1.4) | 1–6 | ||
Their male siblings | n = 20 pairs | 4.5 (1.1) | 2–6 | p = 0.0021 |
Female patients | 3.6 (1.1) | 1–6 | ||
Their female siblings | n = 31 pairs | 4.5 (1.0) | 3–6 | p = 0.0006 |
Patients who received 25 Gy | 3.4 (1.2) | 1–6 | ||
Their siblings | n = 65 pairs | 4.5 (1.1) | 3–6 | p = 0.0001 |
Patients who received 18 Gy | 3.5 (0.9) | 2–6 | ||
Their siblings | n = 20 pairs | 4.3 (1.1) | 3–6 | p = 0.0034 |
Patients aged 0–3 y at diagnosis | 2.9 (1.0) | 1–5 | ||
Their siblings | n = 38 pairs | 4.4 (1.0) | 3–6 | p < 0.0001 |
Patients aged 4–6 y at diagnosis | 3.7 (1.0) | 2–6 | ||
Their siblings | n = 26 pairs | 4.7 (1.1) | 3–6 | p = 0.0003 |
Patients aged ⩾7 y at diagnosis | 4.0 (1.0) | 2–6 | ||
Their siblings | n = 21 pairs | 4.4 (1.2) | 3–6 | p = 0.1823 |
↵2-150 On a six point scale: 1 = lowest; 4 = Dutch population mean; 6 = highest:
(1) Exclusive special education for moderate/severe learning disabilities (mental disabled with low IQ) (in Dutch: MLK or ZMLK and VSO(Z)MLK)
(2) Exclusive special education for mild learning disabilities or behavioural disorders with (sub)normal IQ (in Dutch: LOM, VSO-LOM and IVBO)
(3) Regular secondary school education for lower IQ levels (in Dutch: LBO or VBO)
(4) Regular secondary school education for average IQ levels (= Dutch population mean) (in Dutch: MAVO)
(5) Regular secondary school education for higher IQ levels (in Dutch: HAVO)
(6) Regular secondary school education, higher level preparing for university (A levels, college school) (in Dutch: VWO).