The term "adaptogen" gets used loosely in wellness marketing, but it has a specific origin and a specific definition. It was first proposed by Soviet pharmacologist Nikolai Lazarev in the 1940s and later formalized by researchers Israel Brekhman and Irina Dardymov, who outlined three criteria a substance had to meet to qualify as an adaptogen: it must be non toxic at normal doses, it must produce a nonspecific response that helps the body resist a broad range of stressors rather than targeting one specific system, and it must have a normalizing effect on physiology, meaning it helps the body return to balance rather than overstimulating or sedating it (Brekhman & Dardymov, 1969).
Under that definition, only a small number of botanicals are typically classified as true adaptogens, including ashwagandha (Withania somnifera), rhodiola rosea, Asian and American ginseng (Panax species), and holy basil, also called tulsi. Each has a long history of traditional use, but what distinguishes an adaptogen from a folk remedy is the amount of modern clinical research examining how these plants actually behave in the human body, particularly in relation to the stress response system.
Ashwagandha is probably the most researched adaptogen in recent clinical literature. A randomized, double blind, placebo controlled study published in the Indian Journal of Psychological Medicine gave adults with a history of chronic stress a high concentration ashwagandha root extract daily for sixty days. Compared to the placebo group, participants taking ashwagandha showed a significantly greater reduction in serum cortisol, the body's primary stress hormone, along with lower self reported stress and anxiety scores (Chandrasekhar et al., 2012). Cortisol reduction matters because chronically elevated cortisol has been linked to disrupted sleep, changes in appetite, and reduced resilience to future stressors.
Rhodiola rosea has been studied specifically in the context of fatigue related to stress rather than baseline mood. A placebo controlled study published in Planta Medica gave participants experiencing stress related fatigue a standardized rhodiola extract over a four week period and found meaningful improvements in fatigue symptoms and certain measures of cognitive function compared to placebo (Olsson et al., 2009). A separate study looked specifically at physicians working night shifts, a population with a very consistent and measurable form of stress induced fatigue, and found that a low, repeated dose of rhodiola improved mental performance during night duty compared to placebo (Darbinyan et al., 2000).
Ginseng, particularly the Panax species used in both Asian and North American traditions, has been studied for its effects on cognitive performance under demanding conditions rather than mood alone. A study published in the Journal of Psychopharmacology gave healthy adults a single dose of Panax ginseng before a sustained mental workload and found improvements in certain measures of cognitive performance, alongside changes in blood glucose regulation during the task, compared to placebo (Reay, Kennedy, & Scholey, 2005). This is part of why ginseng tends to show up in formulas aimed at sustained attention rather than relaxation.
Holy basil, or tulsi, has a somewhat different research profile, with most of the available literature made up of smaller studies and reviews rather than large scale trials. A review published in the Journal of Ayurveda and Integrative Medicine summarized decades of research on tulsi, describing consistent findings around its role in supporting a healthy stress response and general metabolic health, while also noting that much of the existing evidence would benefit from larger, more rigorously controlled human trials (Cohen, 2014). This kind of caveat is common across adaptogen research generally: promising, repeated findings in smaller studies, with a clear need for larger trials to confirm effect sizes.
The proposed mechanism behind adaptogens involves their interaction with the hypothalamic pituitary adrenal axis, commonly called the HPA axis, which is the communication pathway between the brain and the adrenal glands that governs the release of cortisol and other stress mediators. A widely cited pharmacological review in the journal Pharmaceuticals describes how adaptogens appear to help regulate this system and related stress signaling molecules, which may explain their broad, nonspecific effects across different types of stress, whether physical, chemical, or psychological (Panossian & Wikman, 2010). It is worth noting that researchers are still working out the precise cellular pathways involved, and most of the available human studies are relatively short in duration and modest in size.
It is also important to be clear about what adaptogens are not. They are not regulated by the FDA in the same way pharmaceutical drugs are, meaning manufacturing quality and ingredient concentration can vary significantly between brands. They are not a replacement for treatment of a diagnosed medical condition, including clinical anxiety or depression. And individual responses vary considerably based on dose, baseline health, and even the specific extract or plant part used. Anyone who is pregnant, nursing, or taking prescription medication should talk to a healthcare provider before adding any adaptogen to their routine, since some botanicals can interact with medications or hormone sensitive conditions.
This is part of why formulation transparency matters so much. A functional formula is only as good as its dose and its sourcing. When a label lists a proprietary blend without disclosing exact amounts, there is no way to know whether an ingredient is present at a dose that resembles what was actually used in the clinical research, or just present in a trace amount for marketing purposes.
Understanding adaptogens for what they are, and what the current evidence does and does not show, is the first step to using them thoughtfully rather than as a cure all. They are one tool among many, alongside sleep, movement, and stress management, for supporting a body that is asked to handle a lot.