Table 6. Brain regions demonstrating volumetric group differences comparing HC-IBS controlling for total brain volume.
F statistics and q value along with standardized effect size, Cohen’s d, are reported first from the linear contrast analysis (HC-IBS) on the mean volumetric estimates form the general linear model controlling for total brain volume. Due to the direction of the contrast positive effect sizes represent greater volumes in HCs compared to IBS and negative effect sizes represent greater volume in IBS patients. The last two columns of the table indicate results from linear contrasts analyses after adding the square root of trait anxiety and the square root of global early life trauma scores as covariates to the general linear model controlling for TBV. We report whether group differences in regional volume persisted as indicated by q<.05. Y=denotes regional significance (q<.05) after covariate analysis, N denotes lack of significance. It should be noted that neither trait anxiety of early life trauma scores were considered statistically significant covariates (q<.05) but accounted for enough variance to have effect in the models.
Abbreviations: healthy control- HC, IBS –irritable bowel syndrome, FDR-false discovery rate, SE-standard error
| Region of Interest | F (1,198) |
FDR Adjusted p q |
Mean (mm3) |
SE | Mean (mm3) |
SE | Cohen’s d |
Group differences remain after controlling for trait anxiety | Group differences remain after controlling for early life trauma |
|---|---|---|---|---|---|---|---|---|---|
| L superior frontal gyrus | 4.3 | 0.029 | 51401.4 | 307.0 | 50407.2 | 370.0 | 0.30 | Y | N |
| R superior frontal gyrus | 8.5 | 0.006 | 54705.5 | 440.1 | 52689.6 | 530.3 | 0.42 | Y | N |
| L cingulate | 9.5 | 0.006 | 11358.7 | 142.1 | 10673.0 | 171.3 | 0.44 | Y | N |
| Brainstem | 4.9 | 0.024 | 26649.4 | 255.1 | 25766.7 | 307.5 | 0.32 | N | N |
| L insula | 7.6 | 0.008 | 8310.9 | 101.3 | 7874.0 | 122.1 | 0.40 | Y | N |
| R insula | 10.3 | 0.006 | 5510.5 | 87.1 | 5071.9 | 105.0 | 0.46 | Y | N |
| L middle orbital frontal gyrus | 6.5 | 0.012 | 8618.3 | 71.0 | 8335.4 | 85.6 | 0.37 | Y | N |
| R middle orbital frontal gyrus | 5.2 | 0.021 | 9361.6 | 84.0 | 9060.3 | 101.2 | 0.33 | Y | N |
| L gyrus rectus | 7.9 | 0.007 | 2078.9 | 40.8 | 1898.9 | 49.2 | 0.61 | Y | N |
| L hippocampus | 8.6 | 0.006 | 3674.8 | 37.5 | 3502.0 | 45.2 | 0.42 | Y | N |
| R hippocampus | 8.5 | 0.006 | 4008.6 | 30.7 | 3868.9 | 36.9 | 0.42 | Y | N |
| L Putamen | 6.8 | 0.011 | 2909.1 | 59.5 | 2666.5 | 71.7 | 0.38 | Y | N |
| L amygdala | 4.4 | 0.028 | 1224.9 | 24.0 | 1145.4 | 28.9 | 0.31 | Y | N |
| R amygdala | 9.3 | 0.006 | 1219.8 | 25.7 | 1096.7 | 31.0 | 0.44 | Y | Y |
| L post central gyrus | 14.1 | 0.003 | 20134.9 | 220.3 | 21431.5 | 265.5 | −0.54 | Y | Y |