The adaptogenic mechanism
Adaptogens are a class of plant compounds that modulate the body's stress-response system (HPA axis) without producing the sedation of pharmaceutical anxiolytics or the stimulation of caffeine. Ashwagandha's active compounds are withanolides — steroidal lactones that appear to modulate cortisol production at the adrenal cortex level. The effect is bidirectional: low when stressed, high when fatigued — hence "adaptogenic."
What the RCT evidence supports
Lopresti et al. 2019 (Medicine) — 60 adult RCT — found 600mg/day KSM-66 standardized extract over 8 weeks reduced morning cortisol by 23% and perceived stress scores by 44% vs placebo. Chandrasekhar et al. 2012 (Indian Journal of Psychological Medicine) demonstrated similar cortisol-reduction effects in 64 chronically-stressed adults at 300mg twice daily. Multiple smaller trials show sleep-quality + anxiety-symptom improvement at the same dose range.
Standardization matters
Crude ashwagandha root powder varies wildly in withanolide content. Look for products specifying "standardized to ≥5% withanolides" — KSM-66 (the most-studied brand-name extract) is standardized to 5% withanolides. Sensoril is another well-studied standardized extract (10% withanolides). Generic powder without standardization data is essentially a roulette wheel of active dose.
Safety + interactions
Ashwagandha is generally well-tolerated. Reported side effects in trials: occasional GI upset, drowsiness at high doses. Contraindications: pregnancy (insufficient safety data), autoimmune conditions (immunomodulatory effect), and thyroid disease (mild thyroid-stimulating activity at clinical doses — may help hypothyroid but worsen hyperthyroid). Avoid combination with sedatives + immunosuppressants without medical guidance.
Primary sources: Lopresti AL et al. 2019 (Medicine) — PubMed; Chandrasekhar K et al. 2012 (Indian J Psychol Med).