← Ashwagandha

What It Is and How It Works

Ashwagandha's adaptogenic properties and its effects on cortisol and the stress response

Ashwagandha (Withania somnifera) is an herb used in traditional Ayurvedic medicine for thousands of years. It belongs to a class of herbs called adaptogens, which help the body manage stress. Modern research suggests it can lower cortisol levels and reduce feelings of anxiety and stress [1].

The root extract is the most commonly studied part of the plant. It is generally considered safe for most adults when taken in recommended doses for up to a few months.

Ashwagandha's classification as an adaptogen means it helps normalize the body's physiological response to stressors rather than pushing it in one direction [1]. The plant contains a group of bioactive compounds called withanolides -- steroidal lactones that are believed to drive most of its pharmacological effects.

The primary mechanism involves the hypothalamic-pituitary-adrenal (HPA) axis, the body's central stress response system. In a randomized, double-blind trial, participants taking 240 mg of ashwagandha extract daily for 60 days showed significant reductions in morning cortisol compared to placebo [2]. Cortisol, the body's primary stress hormone, is normally elevated during chronic stress and contributes to downstream metabolic and immune disruption.

Ashwagandha also appears to modulate GABAergic signaling, which may partially explain its anxiolytic (anti-anxiety) effects [3]. This dual action on the hormonal stress axis and neurotransmitter systems distinguishes it from single-mechanism anxiolytics.

HPA Axis Modulation and Cortisol Reduction

The most robust evidence for ashwagandha centers on its effects on cortisol and perceived stress. Chandrasekhar et al. (2012) conducted a 60-day RCT with 64 subjects using 300 mg twice daily of a high-concentration full-spectrum root extract. The treatment group showed a 27.9% reduction in serum cortisol levels (p < 0.0006) and significant reductions on the Perceived Stress Scale compared to placebo [3].

Lopresti et al. (2019) corroborated these findings using 240 mg/day of a standardized extract (Shoden, 35% withanolide glycosides). Salivary cortisol decreased significantly in the ashwagandha group versus placebo, alongside improvements on the Hamilton Anxiety Rating Scale (HAM-A) and the Depression, Anxiety and Stress Scale (DASS-21) [2].

Adaptogenic Mechanism

The adaptogenic model proposes that ashwagandha modulates the stress response at multiple points [1]:

  • HPA axis: Reduces excessive cortisol output under chronic stress without suppressing acute cortisol responses needed for normal function.
  • GABAergic system: Withanolides demonstrate GABA-mimetic activity, contributing to anxiolysis and improved sleep onset.
  • Oxidative stress: Withaferin A and other withanolides exhibit antioxidant activity, reducing stress-induced reactive oxygen species in neural tissue.

Salve et al. (2019) demonstrated dose-dependent effects in a study comparing 250 mg/day and 600 mg/day of ashwagandha root extract over 8 weeks. Both doses significantly reduced PSS scores, but the 600 mg dose produced greater reductions in serum cortisol (p < 0.001) [4]. Sleep quality, measured by the Pittsburgh Sleep Quality Index, also improved significantly at both doses.

Safety Profile

Systematic reviews report that ashwagandha is generally well-tolerated at doses of 250-600 mg/day for up to 12 weeks [1]. The most commonly reported adverse effects are mild gastrointestinal symptoms. However, ashwagandha may affect thyroid hormone levels and should be used cautiously in individuals with thyroid disorders or those taking thyroid medications.

References

  1. An Overview on Ashwagandha: A Rasayana (Rejuvenator) of AyurvedaSingh N, Bhalla M, de Jager P, Gilca M. African Journal of Traditional, Complementary and Alternative Medicines, 2011. PubMed 23439798 →
  2. An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled studyLopresti AL, Smith SJ, Malvi H, Kodgule R. Medicine, 2019. PubMed 32021735 →
  3. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adultsChandrasekhar K, Kapoor J, Anishetty S. Indian Journal of Psychological Medicine, 2012. PubMed 23125505 →
  4. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical StudySalve J, Pate S, Debnath K, Langade D. Cureus, 2019. PubMed 28471731 →

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