Homeostasis: definition and its link with the endocannabinoid system

The term "homeostasis" comes from the Greek hómoios (similar) and stásis (stable state). It was introduced by the American physiologist Walter Cannon in 1929 to describe what Claude Bernard had called, half a century earlier, the "fixity of the internal milieu". The idea is simple: every living being must keep certain internal parameters within a narrow range in order to function properly.

A few concrete examples. Human body temperature hovers around 37 °C: in heat, sweating and cutaneous vasodilation shed the excess; in cold, shivering and vasoconstriction limit the losses. Blood pH stays stable between 7.35 and 7.45 thanks to biochemical buffers. Blood sugar is held steady by the interplay of insulin and glucagon. Cellular hydration is regulated by the kidneys and antidiuretic hormones.

Homeostasis works on a principle of negative feedback. A sensor (a sensory receptor, a specialised cell) detects a variation. The information is passed to an integrating centre (often the hypothalamus for the major physiological variables). A response is triggered to bring the variable back to its set point. Once balance is restored, the signal switches off.

Several systems take part in this regulation: the autonomic nervous system (sympathetic, parasympathetic), the endocrine system (thyroid, adrenal and pituitary hormones), the immune system, and the renal, respiratory and digestive systems. All of them communicate constantly to keep the internal milieu within limits compatible with cellular life.

Uncovered gradually from the late 1980s onwards, the endocannabinoid system (ECS) is one of the largest cell-signalling systems in the body. It has three components.

• Receptors: chiefly CB1 (concentrated in the central nervous system) and CB2 (found in immune cells, the spleen and peripheral organs). Other receptors (TRPV1, PPAR, GPR55) are also involved.
• Endogenous ligands known as endocannabinoids: the two main ones are anandamide (AEA) and 2-arachidonoylglycerol (2-AG), both derived from membrane fatty acids.
• Enzymes that synthesise and break down those ligands (FAAH for anandamide, MAGL for 2-AG).

According to the Inserm dossier on endocannabinoids, this system is involved in regulating appetite, sleep, pain, mood, memory, immune function and thermoregulation. Its main function, as formulated in the literature, is precisely to contribute to homeostasis.

Cannabidiol does not act like THC. THC binds directly to the CB1 receptors of the brain, which is what produces its psychoactive effect. CBD, by contrast, has a very low affinity for CB1 and CB2; it acts indirectly: it modulates the FAAH enzyme (slowing the breakdown of anandamide), interacts with the serotonergic 5-HT1A receptors, and activates the TRPV1 receptors.

This modulating action is the scientific argument often invoked to describe CBD as a "support" for the endocannabinoid system. A caveat, however: the clinical translation of these mechanisms in humans remains insufficiently documented. The EFSA has authorised no health claim for CBD. The ANSES even raised questions in 2025 about the safety of CBD for human reproduction, proposing to the ECHA a category 1B classification, "presumed toxic to reproduction".

In French law, no brand may claim that CBD "regulates homeostasis", "relieves pain" or "reduces anxiety". These are medical or health claims requiring an authorisation under European regulation EC no. 1924/2006, an authorisation that does not exist for cannabidiol.

What a consumer can do: fold a CBD product into a wellbeing routine (an evening ritual, a pause in the day, a relaxation habit), while respecting the usual precautions. What they cannot do: substitute a wellbeing CBD for medical treatment, expect a defined therapeutic effect, or presume it is harmless for women who are pregnant or breastfeeding.

As the ANSES pointed out in its 2024 opinion, the available toxicological data call for caution. CBD remains not advised for women who are pregnant, breastfeeding or of childbearing age, for minors, or for people on medical treatment (documented interactions with several medicines, notably anticoagulants and antiepileptics).

CBD is not a medicine. For any question relating to a physiological disorder, consult a healthcare professional.

• Homeostasis is the body's capacity to maintain a stable internal balance (Walter Cannon, 1929).
• The endocannabinoid system (CB1 and CB2 receptors and endocannabinoids) takes part in that regulation.
• CBD indirectly modulates this system, without binding to it the way THC does.
• No health claim is authorised for CBD in France or in Europe.
• For wellbeing use only, never as a substitute for medical treatment.

• EFSA Journal 2026 — Update statement CBD novel food — primary
• ANSES — Press release, 19 June 2025, on the reprotoxic classification of CBD (PDF) — primary
• ANSES — Opinion, referral no. 2024-SA-0040 — primary