If you spend enough time in medicine, or living with a difficult condition, you notice a pattern.
The patient with migraines also has IBS. The patient with fibromyalgia also has anxiety. The person with treatment-resistant depression also has trouble sleeping and unexplained chronic pain. The veteran with PTSD develops migraines they never had before. These conditions cluster. They often affect the same people. They frequently defy conventional treatment. And they have historically shared one more thing — the frustrating experience of being told, in various ways over the years, that the problem is in the patient’s head.
For decades, the clustering was mostly attributed to bad luck or coincidence, or when a common thread was sought, to something like stress or personality. But over the past twenty years, a different possibility has been building in the scientific literature — one that argues these conditions may share an underlying biological mechanism. Not a personality. Not a psychosomatic quirk. An actual, physiological deficiency in one of the body’s most important regulatory systems.
The theory is called clinical endocannabinoid deficiency, or CED. And it is where this entire series has been quietly heading.
What This Series Has Been Building Toward
Over the previous six installments, we have looked at how the endocannabinoid system relates to some of the body’s most important chemical messengers. In each case, we found a different kind of relationship.
With endorphins, we saw a case of mistaken identity — the runner’s high has more to do with endocannabinoids than the endorphin pathway most people credit. With oxytocin, we saw a partnership — oxytocin triggers anandamide release, and social bonding becomes rewarding in part because of that endocannabinoid signal. With dopamine, we saw a modulator — the endocannabinoid system shapes when and how dopamine is released in the reward circuits of the brain. With serotonin, we saw direct binding — CBD engages serotonin receptors in a way few other plant compounds do. With GABA, we saw the brake system — and how CBD boosts inhibitory signaling in the brain in ways that help explain its role in seizure control. With cortisol, we saw the feedback loop — the endocannabinoid system is one of the mechanisms cortisol uses to turn its own release off.
Six pieces. Six different systems. Six different windows into the same underlying network. The pattern is not a coincidence. The endocannabinoid system reaches into nearly every regulatory function the body performs.
Which raises an obvious question. If the endocannabinoid system is this fundamental — if it regulates mood, pain, sleep, stress, appetite, immune function, and reward — what happens to people whose endocannabinoid systems don’t work well?
That is the question CED tries to answer.
The Theory, in Plain Terms
Clinical endocannabinoid deficiency was first proposed in 2001 by Ethan Russo, a neurologist and one of the most prolific researchers in modern cannabinoid medicine. Russo revised and expanded the theory in a landmark 2016 paper published in Cannabis and Cannabinoid Research, titled “Clinical Endocannabinoid Deficiency Reconsidered.” The theory rests on an analogy that is worth spelling out.
Modern medicine has long recognized that certain conditions involve deficiencies in specific neurotransmitter systems. Parkinson’s disease involves a deficiency of dopamine in the substantia nigra. Alzheimer’s disease involves a deficiency of acetylcholine. Many forms of depression are treated by boosting serotonin and norepinephrine. In each case, a condition emerges — in whole or in part — because a specific chemical signaling system is not producing enough of what the body needs.
Russo’s proposal was straightforward: given how broadly the endocannabinoid system regulates human physiology, it would be strange if a comparable deficiency did not also exist for endocannabinoids. And when he looked at conditions that had proven especially difficult to treat, that clustered together in the same patients, and that produced patterns of symptoms consistent with endocannabinoid system dysfunction — hyperalgesia, central sensitization, sleep disruption, mood disturbance, digestive symptoms — he found candidates.
The base hypothesis of CED is that all humans have an underlying endocannabinoid tone, reflecting the levels of anandamide and 2-AG, the density and function of CB1 and CB2 receptors, and the activity of the enzymes that build and break down these molecules. When that tone is intact, the body’s regulatory systems function within normal ranges. When that tone drops — because of genetics, chronic stress, trauma, poor diet, sedentary living, medications, or aging — the systems that endocannabinoids regulate begin to run out of tune. And the specific way they run out of tune depends on which systems are most vulnerable in that person.
The Three Canary Conditions
The strongest evidence for CED, per Russo’s 2016 review, comes from three conditions.
Migraine. Chronic migraine sufferers show measurably lower anandamide levels in their cerebrospinal fluid than people without migraine. Multiple studies have documented reduced endocannabinoid signaling in migraine populations, along with changes in the enzymes that regulate endocannabinoid levels. Migraine has long been described as a disorder of hyperexcitability in specific brain circuits — exactly the kind of imbalance the endocannabinoid system normally helps to modulate. Cannabis has one of the longest documented histories of any migraine treatment, with medical use extending back thousands of years across multiple cultures.
Fibromyalgia. Fibromyalgia is characterized by widespread chronic pain, fatigue, sleep disturbance, cognitive symptoms, and a nervous system that appears to have become sensitized to signals that would not normally register as painful. Research has documented reduced endocannabinoid levels in fibromyalgia patients, and a growing number of clinical studies have found improvement in fibromyalgia symptoms with cannabinoid-based treatment. Fibromyalgia was, for decades, dismissed as psychosomatic. The endocannabinoid framework has been part of what is finally moving the condition into a place of biological legitimacy.
Irritable bowel syndrome (IBS). IBS involves altered gut motility, visceral pain sensitivity, and communication between the gut and the brain — all functions the endocannabinoid system regulates. Genetic variants in the FAAH gene, which controls the breakdown of anandamide, have been associated with IBS. The endocannabinoid system’s heavy presence in the gut, combined with the pattern of symptoms IBS produces, makes it one of the strongest CED candidates. Beyond the endocannabinoids themselves, other compounds in cannabis — particularly the terpenes that shape its aromatic and physiological profile — appear to play supporting roles in gut regulation.
These three conditions overlap significantly. A person with one is far more likely than the general population to have another. They cluster together in the same patients. They share treatment resistance. They share, in Russo’s framing, a common underlying pattern that is difficult to explain unless something more fundamental is going on beneath all three.
The Expanding List
Since Russo’s 2016 paper, additional conditions have been added to the CED conversation on the basis of accumulating evidence:
Post-traumatic stress disorder. As discussed in the cortisol installment, brain imaging work by Alexander Neumeister and colleagues has documented reduced anandamide levels and compensatory increased CB1 receptor density in people with PTSD. This is now some of the strongest human evidence for endocannabinoid dysfunction in a specific psychiatric condition, and cannabinoid therapies for PTSD are among the most active areas of clinical research in the field.
Certain forms of anxiety and depression. Chronic stress reduces CB1 receptor expression in the stress centers of the brain. Reduced anandamide predicts increased stress-induced anxiety in animal models. Some depression research has begun looking at endocannabinoid dysfunction as a potential mechanism in cases that do not respond well to conventional treatment.
Motion sickness, autism spectrum conditions, some forms of epilepsy, multiple sclerosis, interstitial cystitis, and neonatal failure to thrive are all mentioned in Russo’s review as conditions where endocannabinoid dysfunction may contribute, based on evidence ranging from suggestive to substantial.
CED is not a diagnostic category. It is a hypothesis that a shared underlying mechanism may explain a cluster of conditions that have historically been treated separately. But the fact that the same interventions — cannabinoid-based therapies, and lifestyle changes that support endocannabinoid function — often help across this diverse group of conditions is one of the strongest indirect arguments for the theory.
What Causes Endocannabinoid Tone to Drop
If CED is real, the next question is how it develops. The current research points to several contributing factors:
Genetics. Variants in the FAAH gene (which breaks down anandamide) and the CNR1 gene (which encodes the CB1 receptor) affect baseline endocannabinoid tone. Some people are born with genetic profiles that produce lower endocannabinoid signaling. This is part of why some individuals develop CED-linked conditions and others do not, even under similar life circumstances.
Chronic stress and trauma. Extended activation of the stress response degrades the endocannabinoid system over time. CB1 receptor expression declines in the stress centers of the brain. Endocannabinoid production drops. The system loses some of its capacity to regulate what it is meant to regulate. This is one of the mechanisms proposed to link trauma exposure to conditions like PTSD, chronic pain, and functional gastrointestinal disorders.
Diet. Endocannabinoids are synthesized from essential fatty acids — primarily arachidonic acid, which the body makes from omega-6 fatty acids. Producing endocannabinoids also depends on adequate omega-3 fatty acid intake, which supports the receptor systems and modulates inflammation. Diets low in omega-3s, high in processed foods, and lacking in the raw materials of endocannabinoid production tend to correlate with reduced endocannabinoid tone.
Sedentary living. As explored in the endorphins installment, regular physical activity is one of the most reliable ways to increase endocannabinoid signaling. Sedentary lifestyles do the opposite.
Sleep deprivation. Sleep supports the entire regulatory network of the body, and endocannabinoid function is not exempt. Chronic short sleep is associated with reduced endocannabinoid tone.
Aging and certain medications. Both can affect endocannabinoid function through a variety of mechanisms.
What Supports Endocannabinoid Tone
This is the part of the CED story that has real, practical implications for readers, regardless of whether they have any of the conditions we have discussed.
Regular aerobic exercise. A 2022 meta-analysis found consistent increases in anandamide and 2-AG following moderate-to-high intensity exercise across running, cycling, and other modalities, in populations with and without existing health conditions. This is the runner’s high mechanism from installment one, and it is one of the most reliable endocannabinoid boosters available.
Meaningful social connection. As explored in the oxytocin installment, oxytocin-driven endocannabinoid signaling is part of how social bonding produces the rewarding feelings it does. Chronic social isolation is measurably associated with reduced endocannabinoid function.
A diet rich in omega-3 fatty acids. Cold-water fish (salmon, sardines, herring), flaxseed, walnuts, chia seeds, and hemp seeds all provide the building blocks the endocannabinoid system needs. Interestingly, a small amount of dark chocolate — which contains compounds that mimic and preserve anandamide — has been shown in research to modestly support endocannabinoid signaling as well.
Quality sleep. Seven to nine hours, consistent schedule, dark and cool environment. This is unglamorous advice, but the endocannabinoid literature consistently shows that sleep supports the system.
Stress management practices. Meditation, breathwork, yoga, time in nature, and other practices that reduce chronic HPA axis activation help preserve the endocannabinoid tone that chronic stress erodes. This is not a wellness cliché. It is a mechanism-supported intervention.
Phytocannabinoids. For some people, cannabis-derived compounds — CBD, THC, and increasingly the minor cannabinoids — can help compensate for reduced endogenous endocannabinoid function. This is not a first-line intervention, and it is not appropriate for everyone. But for people whose systems are genuinely compromised — often those with the CED-linked conditions discussed above — cannabinoid therapies can be a meaningful part of a broader care approach. This is a conversation worth having with a knowledgeable provider, and one our care team is available for at no cost.
The Honest State of the Science
CED is a hypothesis. It is a productive one — it has driven substantial research, informed the development of new therapeutic targets, and provided a framework that many patients find validating after years of being told their symptoms were not “real.” But it is not yet a diagnostic category. There is no accepted clinical test for it. Evidence is strong for some of the associated conditions (particularly migraine and PTSD) and more preliminary for others.
Some researchers argue that “endocannabinoid tone dysregulation” is a more accurate framing than “deficiency,” because in some conditions the problem is not simply too little endocannabinoid signaling but rather signaling that has become miscalibrated in specific circuits. The distinction matters clinically because it would affect how treatment is designed.
The core insight of CED, however, has proven durable. The endocannabinoid system is fundamental. It is one of the most important regulatory systems in the human body. When it does not function well, the consequences are broad, unpredictable, and often resistant to conventional treatment. And a growing body of research suggests that some of medicine’s most persistent challenges — the treatment-resistant pain syndromes, the poorly understood functional disorders, the conditions where the tests come back normal but the patient is not well — may share this underlying thread.
Why This Matters
There is a reason Realm of Caring exists.
Thirteen years ago, two mothers came together — Heather Jackson and Paige Figi — because their children had run out of options. Their families’ experiences with cannabinoid therapies were not incidental to the science we have covered in this series. They were living examples of what happens when the endocannabinoid system is engaged in ways conventional medicine had not yet been paying attention to.
Since then, we have supported more than 100,000 clients worldwide, contributed to legislative change in twenty-two states, and built the largest observational cannabis research program in the United States in partnership with Johns Hopkins University. We have done this work because the people who come to us are, by and large, people whose conditions fit the pattern this series has described. They have exhausted the standard approaches. They have often been dismissed. And they have found, in cannabinoid-based care and in a broader understanding of the endocannabinoid system, something that begins to make sense.
CED is not a promise of a cure. It is a framework. But it is a framework that has changed how a growing body of researchers, clinicians, and patients think about a set of conditions that had, for a long time, been thought of as unrelated. The endocannabinoid system runs through all of them. And supporting that system — through lifestyle, through care, through the informed use of cannabinoid therapies when appropriate — is one of the most promising directions in a field that has needed better directions for a long time.
If you are exploring what any of this might mean for you, our care team is available worldwide at no cost. If you are interested in contributing to the science of what we have been describing, our Observational Research Registry — a longitudinal study conducted in partnership with Johns Hopkins University — welcomes patients from anywhere in the world. And our Research Library holds more than 800 peer-reviewed studies for anyone who wants to go deeper.
Thank you for following along with this series. What we have covered is a small window into a system that is still, in many ways, at the beginning of what we understand about it. The next decade of research will almost certainly change and expand what we have written here. That is how science works. But the core story — that your body has an endogenous system that regulates the most important functions of being alive, and that this system responds to how you live, and that cannabis-derived compounds interact with it in ways that can be therapeutic when applied with care — is not going to be overturned. It is going to keep unfolding.
We are grateful to be part of that unfolding, and to have you as part of the community that is unfolding it with us.
