Table 5.

Meta-analyses examining associations between childhood trauma and neuroimaging measures in clinical and non-clinical populations.

Author	Population	Measure	Findings
Nikolova et al. (2021)	Psychiatric disorders	Gut microbiota alterations across psychiatric disorders	Analysis of alpha diversity showed a significant decrease in richness (number of species) across all observed species compared to controls for pooled analysis of all psychiatric disorders (k = 20, SMD = −0.26 (95% CI: −0.47 to −0.06) p = 0.01) and for sub-analyses examining bipolar disorder (k = 3, SMD = –0.61 (95% CI: –1.19 to –0.03), but no significant differences in sub-analyses comparing patients with MDD (k = 6, SMD = –0.16 (95% CI: –0.58 to 0.27) or schizophrenia and psychosis (k = 4, SMD = –0.04 (95% CI: –0.31 to 0.24) with controls. Studies examining Chao1 showed a significant decrease relative to controls when data were pooled across all psychiatric disorders (k = 26, SMD = −0.5 (95% CI: −0.79 to −0.21) p = .001), and significant decreases for bipolar disorder (k = 4, SMD = –0.53 (95% CI: –1.01 to –0.05) and anorexia nervosa (k = 4, SMD = –0.86 (95% CI: –1.52 to –0.21). No significant differences were observed for sub-analyses comparing controls with MDD (k = 6, SMD = –0.34 (95% CI: –1.08 to 0.40) or schizophrenia and psychosis patients (k = 7, k = –0.58 (95% CI: –1.29 to 0.12), Compared to controls, no significant differences in the Shannon index were observed across all psychiatric disorders (k = 29, SMD = −0.12 (95% CI: −0.27 to 0.03) p = .11), MDD (k = 11, SMD = –0.28 (95% CI: –0.62 to 0.06), bipolar disorder (k = 4, SMD = 0.09 (95% CI: –0.43 to 0.62), or schizophrenia and psychosis (k = 8, SMD = –0.02 (95% CI: –0.20 to 0.17). No differences compared to controls in the Simpson index were observed across all psychiatric disorders (k = 11, SMD = 0.04 (95% CI, −0.13 to 0.21) p = .66) MDD (k = 5, SMD = 0.14 (95% CI: –0.14 to 0.43), or bipolar disorder (k = 3, SMD = –0.03 (95% CI: –0.34 to 0.28). Phylogenetic diversity was significantly reduced when data from all psychiatric patients were compared with controls (k = 10, SMD = −0.24 (95% CI, −0.47 to −0.0012) p = .049), but not in sub-analyses examining MDD (k = 4, SMD = –0.42 (95% CI: –0.96 to 0.13) or schizophrenia and psychosis (k = 3, SMD = –0.01 (95% CI: –0.22 to 0.20).
Safadi et al. (2022)	Severe mental illness	Biomarkers of gut dysbiosis differences in severe mental illness	A combined analysis of BPD and MDD samples showed significant increases in zonulin (k = 4, SMD = 0.97 (95%Cl: 0.10 to 1.85) p = 0.03) relative to controls. Antibodies to endotoxins were significantly elevated in BPD (k = 2, SMD = 0.72 (95% CI: 0.54 to 0.90), MDD (k = 2, SMD = 0.77 (95% CI: 0.43 to 1.12), but not schizophrenia (k = 3, SMD = 1.16 (95% CI: -0.48 to 2.81). Soluble CD14: significantly elevated relative to controls in BPD (k = 3, SMD = 0.61 (95% CI: 0.15 to 1.07) but not schizophrenia (k = 3, SMD = 0.29 (95% CI: -0.24 to 0.82). Alpha-1-antitrypsin was significantly elevated in MDD (k = 3, SMD = 0.94 (95% CI: 0.35 to 1.53) and schizophrenia (k = 3, SMD = 1.79 (95% CI: 1.16 to 2.42) relative to controls. Intestinal fatty-acid binding protein showed no significant differences in comparisons between MDD and controls (k = 3, SMD = 0.30 (95% CI: -0.21 to 0.82).

Abbreviations: k: number of effect sizes included in analysis; SMD: standardised mean difference; CI: confidence interval; r: correlation coefficient; MDD: major depressive disorder; BPD: bipolar disorder.