Cause and Effect, by Rachel Yehuda.

Rachel Yehuda noticed that people with post traumatic stress disorder have lower levels of cortisol. Which is contrary to what you would expect, given that cortisol is “the stress hormone”.

To work out why, she has to convince a community of Holocaust survivors to subject themselves to scientific study.

Cause and Effect.

http://www.storycollider.org/stories/2016/9/22/rachel-yehuda