Results from several clinical trials suggest that ashwagandha extracts may help reduce stress and anxiety. A 2021 systematic review identified seven studies that investigated the use of ashwagandha to treat stress and anxiety [8]. A total of 491 adults, all from India, with either self-reported high stress and anxiety or a diagnosed anxiety disorder, were randomized to take ashwagandha or placebo for 6 to 8 weeks. Six of the studies used extracts made from ashwagandha root alone (three studies, KSM-66), root and leaf (two studies, Sensoril or Shoden), or unspecified parts (one study), while the seventh study used dried root powder made into granules. The ashwagandha dose varied from 240 to 1,250 mg/day of extract or 12,000 mg/day of whole root granules, which is equivalent to 6,000 mg of root powder. Overall, the studies found that ashwagandha significantly reduced stress and anxiety levels (subjectively measured by validated rating scales), reduced sleeplessness and fatigue, and reduced serum cortisol levels (a stress hormone) when compared with placebo. In several studies, the benefits appeared to be greater with doses of 500 to 600 mg/day than with lower doses.

Results from most of the studies published after this 2021 review also suggest that ashwagandha has a beneficial impact on perceived stress [9-17]. For example, one clinical trial conducted in Florida included 60 men and women (mean age 34 years) who reported experiencing stress. Participants took capsules that contained 225 mg/day or 400 mg/day of a proprietary ashwagandha root and leaf extract (NooGandha) or placebo for 30 days [9]. Compared with participants in the placebo group, those in both ashwagandha groups reported positive effects on stress, anxiety, depression, and food cravings as measured by validated rating scales. In addition, participants who took the 225-mg dose had lower saliva cortisol levels than those in the placebo group.

At two health centers in India, 130 healthy men and women age 20 to 55 years with self-reported stress were randomized to take a sustained-released ashwagandha root extract (Prolanza) or placebo for 90 days [10]. The extract was standardized to contain 15 mg withanolides per 300-mg capsule, and participants took one capsule daily. Compared with those who received placebo, participants who took ashwagandha extract reported improvements in stress levels and sleep quality as measured by validated rating scales. They also had lower serum cortisol levels. In addition, participants reported improvements in psychological well-being, memory, and focus. Another study in India randomized 54 participants with mild to moderate stress and anxiety to receive either ashwagandha root extract (Shagandha) or placebo [14]. The participants in the ashwagandha group were given tablets that were standardized to contain 2.5% withanolides; each tablet included 500 mg of the root extract and 5 mg of piperine. At day 60, participants in the ashwagandha group had significantly lower scores for stress and anxiety on two validated rating scales than those in the placebo group. In addition, the quality of life scores increased significantly for people in the ashwagandha group between baseline and day 60, and the researchers noted improvements in multitasking and concentration among the participants in this group.

At the University of Colorado, Colorado Springs, 60 students (age 18–50 years) were randomized to take an ashwagandha root extract (Gaia Herbs) or placebo for 30 days in a double-blind trial [11,12]. The extract contained 2.5 mg withanolides per 350-mg capsule, and participants took two capsules daily. The investigators gathered qualitative, subjective information from participants during daily check-ins and focus groups. Participants who took ashwagandha root extract reported increased well-being, including a sense of calm; improved energy levels; heightened mental clarity; and enhanced sleep quality. While the descriptions of stress were comparable in both groups, participants who took ashwagandha were more likely to describe their stress as manageable compared with those taking placebo.

Another randomized clinical trial included 120 healthy men and women (mean age 54–55 years) who were overweight or mildly obese and experiencing low energy and fatigue [17]. Participants took an ashwagandha root extract (Witholytin, which contains 200 mg hydroalcoholic extract of ashwagandha root standardized to 1.5% withanolides) or placebo twice daily for 12 weeks. Compared with placebo, ashwagandha did not reduce perceived stress, but it did reduce fatigue.

A daily dose of 300 to 600 mg ashwagandha root extract (standardized to 5% withanolides) is provisionally recommended for the treatment of generalized anxiety disorder by an international taskforce created by the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) [18]. The taskforce issued this recommendation in 2022, and they noted that more research is needed to support a stronger recommendation.