I appreciate that people are looking into this, and I think more research of this kind should be funded. However, one needs to be cautious when claiming an "impairment" in fear regulating regions from a measure of cortical thickness with MRI. For once, there is no evidence that a slightly thinner or larger cortical thickness means better or worse regulation of any kind. Second, morphology studies are susceptible to many sources of biases which are not really addressed in this study. For example, anything that affects hydration levels or causes a redistribution of blood and cerebral spinal fluid volume can lead to significant changes in measures of cortical thickness, since they will change the contrast between gray and white matter that drive cortical thickness measurements.

Changes in thickness have been found even when comparing people scanned in the morning and in the evening [1]. Any drug intervention could be expected to cause physiological changes that could act as confounds. Also, in the discussion one reads: "Interestingly, no lasting effects of combined oral contraceptives (COCs) use were detected when comparing the four groups." This suggests that the changes could be driven by physiological changes instead of permanent changes in brain circuitry.

It would be great to see a follow up study controlling for potential confounding effects (for example, measuring baseline perfusion, blood pressure and controlling for time of day effects and usage of other drugs), and expanding the study with functional tests that involve fear regulation.

[1] https://www.sciencedirect.com/science/article/pii/S105381191...