Table 1. Effect sizes differences between all BD cases and controls (Cohen's d) for the mean volume of each structure controlling for age, sex and intracranial volume.
| BD–CTL (SE) | 95% CI | Percent difference | Z-score | P | I2 | Het. P | # CTL | # BD | Hedges' g | |
|---|---|---|---|---|---|---|---|---|---|---|
| Lateral ventricle | 0.260±0.063 | (0.136–0.384) | 16.098 | 4.111 | 3.93 × 10−5 | 65.4 | 1.64 × 10−6 | 2592 | 1708 | 0.261 |
| Thalamus | −0.148±0.052 | (−0.250 to −0.047) | −1.156 | −2.858 | 4.27 × 10−3 | 48.6 | 6.58 × 10−3 | 2589 | 1702 | −0.147 |
| Caudate | −0.09±0.051 | (−0.190–0.010) | −0.967 | −1.773 | 0.076 | 46.0 | 0.017 | 2586 | 1704 | −0.090 |
| Putamen | −0.001±0.044 | (−0.088–0.085) | 0.054 | −0.034 | 0.973 | 30.2 | 0.073 | 2588 | 1704 | −0.001 |
| Globus pallidus | −0.028±0.057 | (−0.140–0.083) | −0.285 | −0.498 | 0.618 | 57.4 | 1.53 × 10−3 | 2588 | 1707 | −0.028 |
| Hippocampus | −0.232±0.045 | (−0.321 to −0.143) | −2.010 | −5.094 | 3.50 × 10−7 | 33.9 | 0.049 | 2582 | 1705 | −0.232 |
| Amygdala | −0.108±0.040 | (−0.187 to −0.029) | −1.068 | −2.667 | 7.65 × 10−3 | 19.4 | 0.304 | 2590 | 1703 | −0.107 |
| Accumbens | −0.064±0.063 | (−0.187–0.060) | −0.929 | −1.013 | 0.311 | 65.1 | 6.86 × 10−5 | 2567 | 1689 | −0.064 |
| ICV | 0.012±0.055 | (−0.095–0.120) | 0.155 | 0.225 | 0.822 | 52.9 | 1.75 × 10−4 | 2594 | 1710 | 0.012 |
Abbreviations: BD, bipolar disorder; CI, confidence interval; CTL, controls; ICV, intracranial volume. The percent difference is the mean change in volume of a structure in bipolar patients versus controls as a percent of the total volume of the structure in controls. I2 gives the estimate of the total heterogeneity as a proportion of the total variability for each measure. Uncorrected P-values are reported. Effect size differences are considered significant (marked with *) if they exceed P<4.91 × 10-3 (see Methods for threshold determination).