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CHAPTER 3
The volumetric analyses were repeated three times while excluding the patients with a history of using (i) typical antipsychotics (3 PTSD-DID) (supplementary Table S3.1), (ii) anti-epileptics (4 PTSD-DID) (supplementary Table S3.2), and (iii) antidepressants (10 PTSD-DID and 2 PTSD-only) (supplementary Table S3.3). To test the effect of PTSD diagnosis, first volumetric measurements were compared between All-PTSD vs. HC (HC: healthy controls) using analysis of covariance (ANCOVA), with group and MRI center as independent factors and age and parenchymal volume as covariates. The analysis was followed by two-sample t-tests to compare left and right hippocampal volumes separately between: 1) PTSD-DID vs. HC, 2) PTSD-DID vs. PTSD-only, and 3) PTSD-only vs. HC.
When PTSD-DID patients with a history of using typical antipsychotics were excluded (supplementary Table S3.1), the majority of the findings remained significant and only the difference in the right hippocampal global volume in PTSD-DID vs. PTSD-only comparison and right CA1 in the PTSD-DID vs. HC comparison changed from significant to trend levels (p=0.073 and p=0.059, respectively).
After excluding PTSD-DID patients with a history of using anti-epileptics (supplementary Table S3.2), we found that the effect size of group differences for PTSD-DID vs. HC as well as PTSD-DID vs. PTSD-only became larger for right and especially left hippocampal global volumes and the differences between the PTSD-DID and PTSD-only became significant in the bilateral hippocampal global volume and volume of the left CA1, right CA2-3, bilateral CA4-DG, bilateral subiculum. This may indicate that PTSD-DID patients with a history of using anti-epileptic drugs had larger hippocampal volumes compared with those of PTSD-DID patients without a history of using anti-epileptic drugs and therefore resulted in an underestimation of the hippocampal reductions in the PTSD-DID group.
When PTSD-DID and PTSD-only patients with a history of using antidepressants were excluded from the volumetric analyses (supplementary Table S3.3) the results of smaller left and right hippocampal volume in PTSD-DID relative to HC became less significant, which is most likely caused by insufficient statistical power. However, the pattern of differences remained the same.
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