Table 1.
Descriptive statistics with mean and variance comparisons for overall volumes, subcortical volumes, and cognitive tests.
| Measure type | Measure | Female (n = 2,750) |
Male (n = 2,466) |
Mean difference test | Variance Ratio test | ||||
|---|---|---|---|---|---|---|---|---|---|
| M (SD) | M (SD) | t | p | d | BF10 | VR | p | ||
| Overall volumes (cm3) | Total brain volume | 1115.76 (89.68) | 1233.58 (98.31) | −48.91 | ~0.00 | −1.41 | 9.57×10426 | 0.82 | 6.46×10-06 |
| Grey matter volume | 597.02 (47.78) | 643.45 (52.08) | −38.97 | 1.75×10-287 | −1.28 | 1.62×10289 | 0.81 | 3.60×10-06 | |
| White matter volume | 518.85 (47.89) | 589.59 (52.69) | −51.53 | ~0.00 | −1.49 | 1.47×10465 | 0.82 | 7.31×10-06 | |
| Subcortical volumes (cm3) | Left hippocampusa | 3.73 (0.42) | 3.94 (0.46) | −18.91 | 2.69×10-76 | −0.55 | 1.09×1074 | 0.86 | 3.83×10-04 |
| Right hippocampusa | 3.82 (0.42) | 4.04 (0.48) | −18.43 | 1.16×10-72 | −0.54 | 7.97×1070 | 0.77 | 1.16×10-09 | |
| Left accumbensa | 0.49 (0.11) | 0.53 (0.12) | −13.42 | 5.19×10-39† | −0.39 | 2.13×1036 | 0.81 | 2.95×10-06 | |
| Right accumbensa | 0.40 (0.10) | 0.42 (0.11) | −10.64 | 3.82×10−26† | −0.31 | 1.04×1023 | 0.83 | 4.46×10-05 | |
| Left amygdala | 1.21 (0.22) | 1.35 (0.25) | −20.04 | 5.23×10-85† | −0.59 | 4.73×1083 | 0.74 | 5.89×10-12 | |
| Right amygdala | 1.18 (0.24) | 1.31 (0.27) | −17.55 | 2.16×10-66† | −0.51 | 1.60×1064 | 0.79 | 1.54×10-07 | |
| Left caudate | 3.28 (0.38) | 3.54 (0.41) | −23.00 | 3.04×10-110 | −0.66 | 2.70×10108 | 0.85 | 2.38×10-04 | |
| Right caudate | 3.45 (0.40) | 3.72 (0.44) | −22.67 | 2.37×10-107 | −0.65 | 4.08×10105 | 0.84 | 4.46×10-05 | |
| Left palliduma | 1.69 (0.21) | 1.85 (0.22) | −26.64 | 4.87×10-145† | −0.77 | 2.19×10143 | 0.88 | .002 | |
| Right palliduma | 1.74 (0.20) | 1.89 (0.22) | −26.96 | 3.82×10-148† | −0.78 | 8.59×10146 | 0.84 | 1.03×10-04 | |
| Left putamena | 4.61 (0.50) | 5.07 (0.56) | −34.72 | 1.73×10-234† | −1.01 | 1.29×10235 | 0.83 | 1.46×10-05 | |
| Right putamena | 4.64 (0.49) | 5.13 (0.55) | −37.13 | 4.76×10-264† | −1.08 | 3.02×10265 | 0.81 | 1.98×10-06 | |
| Left thalamusa | 7.54 (0.64) | 8.11 (0.72) | −33.73 | 7.76×10-223 | −0.98 | 1.50×10223 | 0.82 | 1.34×10-05 | |
| Right thalamusa | 7.34 (0.62) | 7.92 (0.69) | −35.76 | 2.42×10-247 | −1.03 | 6.62×10247 | 0.83 | 4.46×10-05 | |
| Cognitive tests | Verbal-numerical reasoning (max. score 13) | 6.80 (2.10) | 7.14 (2.13) | −6.21 | 5.77×10-10 | −0.18 | 6.94×106 | 0.97 | .451 |
| Reaction time (ms) | 590.37 (98.04) | 574.71 (100.71) | −7.63 | 2.71×10-14 | −0.21 | 1.30×1011 | 0.92 | .033 | |
Note: Means and SDs are shown prior to adjustment for age and ethnicity; statistical tests are performed after this adjustment. Reaction Time is shown here in raw millisecond units, but was reverse-scored for analysis so that higher scores indicated better performance. Negative t- and d-values mean higher male means. VR = Variance ratio (values < 1 indicate greater male variance). p-values for brain variables corrected for multiple comparisons using the False Discovery Rate correction. BF10 = Bayes Factor indicating the probability of the alternative hypothesis (that there is a sex difference) compared to the null hypothesis (that there is no sex difference).
= significant age-by-sex interaction.
= sex difference in subcortical region still significant after adjustment for total brain volume (see Table S1).