The Annex: 20 rats a group, five in each corner, and a PTSD 'biomarker' that is still a question

The Annex reads the method behind the headline. Today’s: a University of Cincinnati press release saying a stress-hormone pattern “may signal vulnerability” to PTSD in females, and could help explain why women are diagnosed at roughly twice the rate of men¹. The paper, by Emily Devine, James Herman and colleagues, appeared in Frontiers in Cellular Neuroscience².

The design. Young adult Sprague-Dawley rats were first given a mild stressor, six minutes in a light-dark box, and their blood hormone corticosterone was measured at 15, 30, 60 and 120 minutes². Three weeks later half of them went through “single prolonged stress”: two hours of restraint, a 20-minute group swim and ether to unconsciousness, a standard rodent model of trauma². Then came anxiety and fear tests, including how well the animals “unlearned” a fear after the tone stopped predicting a shock². There were 20 animals per group².

The result. In females, those with the strongest hormone response to the mild stressor showed more anxiety-like behaviour, worse fear extinction and stronger return of fear after trauma². Low resting hormone plus a high spike predicted the worst outcomes^1,2. In males, stress reactivity did not predict outcomes in the same way¹.

The footnotes that matter. The headline comparison used only the top and bottom quarters of responders: five animals per group². In the correlation analysis, “none survived” correction for multiple testing, which the authors put down to many variables and a small sample; they then used permutation tests to check the direction of the effects². Males and females were run in separate cohorts three months apart, so, the authors write, “we can only observe differences in stress reactivity within each sex”². Oestrous cycle was not tracked². And the findings are “largely correlational”².

What the authors themselves say. Herman calls the hormone pattern a candidate biomarker, “not a diagnostic test”, and says the work is preclinical¹. The press release’s own FAQ answers “Does this mean there is a blood test for PTSD?” with “Not yet”¹.

For you. This is careful, honest work, and its honesty is in the small print. The useful lesson is not about rats. It is that recovery from fear is a learning process, and learning can be helped. That is why trauma therapies exist, and why early, ordinary support after a bad event is worth giving.