Table 1.
Participant characteristics
| Mean (SD) [range]a | Male controls | Males with autism | Female controls | Females with autism | Statisticsb |
|---|---|---|---|---|---|
| Age, years | 28.2 (5.6) | 27.2 (7.3) | 27.5 (6.5) | 27.8 (7.6) | ns |
| Verbal IQ | 112.7 (9.7) | 114.3 (12.9) | 118.5 (9.6) | 115.8 (13.1) | ns |
| Performance IQc | 118.5 (11.6) | 113.3 (15.0) | 117.0 (9.3) | 110.4 (16.7) | MC > FA (P = 0.021) |
| Full-scale IQc | 117.5 (10.7) | 115.4 (14.1) | 120.2 (8.0) | 114.9 (13.8) | ns |
| Autism Diagnostic Interview-Revisedd | |||||
| Social | – | 18.0 (5.1) [10–27] | – | 16.4 (4.3) [11–26] | ns |
| Communication | – | 15.3 (3.5) [8–22] | – | 13.1 (3.9) [8–22] | MA > FA (P = 0.029) |
| Repetitive, restrictive and stereotyped behaviourc | – | 5.6 (2.5) [2–10] | – | 4.3 (1.7) [2–8] | MA > FA (P = 0.023) |
| Autism Diagnostic Observation Schedule | |||||
| Social interaction + communication total score | – | 8.5 (5.0) [1–17] | – | 4.3 (3.6) [0–13] | MA > FA (P < 0.001) |
| Repetitive, restrictive and stereotyped behaviour | – | 1.0 (1.0) [0–4] | – | 0.1 (0.3) [0–1] | MA > FA (P < 0.001) |
| Autism Spectrum Quotient | 15.6 (6.9) | 32.7 (7.3) | 12.0 (4.8) | 37.5 (6.7) | e |
| Empathy Quotient | 42.7 (11.9) | 19.7 (10.1) | 53.5 (9.5) | 19.5 (7.5) | e |
| TAS-20 | 42.5 (10.3) | 61.4 (9.2) | 41.1 (9.2) | 65.5 (8.1) | e |
| Eyes Test | 27.0 (3.4) | 22.8 (5.8) | 28.8 (2.3) | 23.4 (6.2) | e |
| Grey matter, cm3 | 914 (78) | 940 (105) | 824 (81) | 845 (72) | f |
| White matter, cm3 | 510 (38) | 513 (56) | 448 (53) | 465 (47) | f |
| CSF, cm3 | 270 (59) | 264 (63) | 236 (53) | 227 (45) | f |
| Total brain volume, cm3 | 1424 (103) | 1453 (154) | 1272 (124) | 1310 (107) | |
| Total intracranial volume, cm3 | 1695 (135) | 1717 (177) | 1508 (151) | 1537 (118) |
n = 30 per group. ns = non-significant (P > 0.05).
TAS-20 = Toronto Alexithymia Scale; Eyes Test = Reading the Mind in the Eyes Test.
Total intracranial volume = total brain volume + CSF; total brain volume = grey matter + white matter.
aFor Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule scores.
bIndependent sample t-tests between any two groups, except non-parametric Mann-Whitney tests for Autism Diagnostic Observation Schedule algorithm scores (distribution significantly deviant from normal). All P-values were not corrected for multiple comparisons.
cLevene’s Test for Equality of Variances showed significant non-equal variances, therefore equal variance was not assumed.
dn = 30 for males with autism, n = 28 for females with autism.
eSee Supplementary material and Supplementary Fig. 1 for statistical details of group differences.
fSee ‘Results’ section for statistical details of group differences.