Ashwagandha did not beat placebo for stress in one 12-week trial
Over 12 weeks in 120 overweight adults aged 40 to 75, stress scores fell about as far on placebo as on ashwagandha. Fatigue fell further on ashwagandha than on placebo.
What the study found
Placebo matched ashwagandha on stress in older, overweight adults
Over 12 weeks in 120 overweight adults aged 40 to 75, stress scores fell 39% on 400 mg of ashwagandha a day and 36% on placebo, too close to call a difference. Fatigue fell 46% against 31% on placebo. Whether ashwagandha eases stress may depend on who is taking it.
The caveat · Placebo fell far more than usual
Placebo groups in earlier ashwagandha stress trials barely moved, falling around 5.5%, so a 36% placebo fall may be what hid the difference here rather than a weaker herb. Cortisol was not measured, so this says nothing about the hormone. The fatigue result was one secondary outcome among many measured, which makes a chance finding more likely. The trial was paid for by the extract's maker.
What we don't know
Whether ashwagandha's edge on stress survives a strong placebo response is open. Pooled trials found it beat placebo, but in older, overweight adults the placebo group improved by a third and matched it.