"Adaptogen" describes a category of herbs proposed to help the body resist stress-related dysfunction, and among them, ashwagandha and holy basil (tulsi) have accumulated the most substantial randomized controlled trial evidence for measurable stress and cortisol outcomes, distinct from many other herbs marketed under the same umbrella term with far less data behind them.
Quick Facts
- Ashwagandha: Reduced cortisol and stress scores in a 15-study meta-analysis of 873 patients
- Holy basil: An 8-week, 100-subject trial found significant reductions in stress, anxiety, and depression scores
- Rhodiola: Some trial support for fatigue-related stress, generally smaller studies than ashwagandha or holy basil
- Timeline: Most trials measure effects after 6-8 weeks of consistent use
- Mechanism overlap: Both ashwagandha and holy basil show cortisol-lowering effects, though through somewhat different proposed pathways
Ashwagandha: The Most-Studied Option
A 2025 meta-analysis of 15 studies and 873 patients found ashwagandha significantly reduced both perceived stress and cortisol at 8 weeks, along with reduced anxiety scores on standardized rating scales. It remains the most extensively studied adaptogen for stress specifically, though a separate, more narrowly focused meta-analysis found it reduced cortisol more reliably than subjective stress ratings, a nuance worth knowing rather than expecting uniform results. See our full Ashwagandha guide.
Holy Basil: A Strong Second Option
A randomized, double-blind, placebo-controlled trial giving 300mg of holy basil extract twice daily for 8 weeks to 100 subjects with generalized stress symptoms found statistically significant reductions in stress, anxiety, and depression scores, along with improved sleep quality, compared to placebo. Separately, holy basil buffered physiological stress responses in an acute stress test, showing lower salivary cortisol, alpha-amylase, and blood pressure compared to placebo. A 2017 review examining 24 human studies found consistent improvements in stress markers, mood, and cognitive function. See our full Holy Basil guide.
What the Research Actually Shows
Ashwagandha for cortisol and stress reduction. Evidence level: Established. Large, consistent meta-analysis support.
Holy basil for stress, anxiety, and mood. Evidence level: Promising. Strong individual trial and review support, though a somewhat smaller cumulative evidence base than ashwagandha.
Safety & Who Should Be Cautious
Ashwagandha should be used cautiously by those with autoimmune thyroid conditions or during pregnancy. Holy basil may lower blood sugar and interact with diabetes or blood-thinning medications. Both are generally well tolerated at standard studied doses otherwise.
ⓘ Ashwagandha has the largest cumulative evidence base among adaptogens for stress, with holy basil close behind and showing strong individual trial results of its own. Both typically require 6-8 weeks of consistent use to see measurable effects.
Frequently Asked Questions
What is the best adaptogen for stress?
Ashwagandha has the largest and most consistent body of randomized trial evidence, with holy basil showing strong supporting results as well.
How long do adaptogens take to work?
Most clinical trials measure effects after 6-8 weeks of consistent daily use, not immediate onset.
Can I take ashwagandha and holy basil together?
Both are generally well tolerated individually; combining them hasn't been extensively studied together, so starting with one and monitoring your response is a reasonable approach.
Do adaptogens lower cortisol or just make you feel less stressed?
Both effects are documented, though some research finds cortisol reduction more consistent than changes in subjective stress ratings, particularly for ashwagandha.
Scientific References
- "Effects of Ashwagandha Supplements on Cortisol, Stress, and Anxiety Levels in Adults: A Systematic Review and Meta-Analysis." BJPsych Open, 2025.
- Sarris, J., Cox, K. H. M., Camfield, D., et al. "Effects of an Ocimum Tenuiflorum (Holy Basil) Extract on Stress, Mood, and Sleep in Adults Experiencing Stress." Frontiers in Nutrition, 2022;9:965130.
Disclaimer
This article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. It does not constitute medical advice. Always consult a qualified healthcare provider before beginning any new supplement regimen.
