Ashwagandha lowered cortisol and stress in highly stressed adults
Across nine trials in 558 people, pooled in one review, cortisol fell against placebo, and so did self-rated stress and anxiety. The people studied were already highly stressed when they started.
What the study found
Ashwagandha lowered cortisol in nine pooled trials of 558 people
Cortisol was not the only thing that moved: self-rated stress and clinician-rated anxiety fell with it. The nine trials are one review's pooled set; a second review agreed without pooling. One trial in that second review saw DHEA-S, another hormone the adrenal glands make, fall too.
The caveat · Extract and dose varied by trial
The trials recruited adults who already described themselves as highly stressed, so the same fall may not appear in someone whose cortisol starts out ordinary. Four of the nine trials reported mild-to-moderate side effects. Extract and dose differed from trial to trial, so the pooled result describes no one product. The second review's two studies that measured cortisol in saliva rather than blood disagreed, one finding no change at all. In a later 12-week trial of older, overweight adults, stress scores fell about as far on placebo as on ashwagandha, and cortisol was not measured, so the self-rated stress part of this result is less settled than the cortisol part.