Ashwagandha 

Studies have shown that ashwagandha significantly reduces stress and anxiety levels, as measured by validated rating scales. It also improves sleep quality and reduces fatigue. Furthermore, it lowers serum cortisol levels, a stress hormone, compared to a placebo.

Ashwagandha is best known for its stress-reducing effects. The medicinal herb helps lower cortisol levels, a hormone produced by the adrenal glands in response to stress. Specifically, daily doses of 225–400 milligrams for a month have been shown to significantly lower cortisol levels.

Research suggests that extracts of ashwagandha may lower stress, anxiety, and cortisol levels. A task force, formed by the World Federation of Societies of Biological Psychiatry and the Canadian Network for Mood and Anxiety Treatments, provisionally recommends specific daily doses of ashwagandha root extract for treating generalized anxiety disorder. However, it notes that it cannot provide a stronger recommendation without further data.