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Neuroendocrinology Letters Nos.1/2 Feb-Apr Vol.25, 2004 Copyright © Neuroendocrinology Letters ISSN 0172–780X www.nel.edu
Neuroendocrinology Letters Nos.1/2, Feb-Apr Vol.25, 2004
Copyright © 2004 Neuroendocrinology Letters ISSN 0172–780X www.nel.edu
Clinical Endocannabinoid Deciency (CECD):
Can this Concept Explain Therapeutic Benets of Cannabis in
Migraine, Fibromyalgia, Irritable Bowel Syndrome and other
Treatment-Resistant Conditions?
Ethan B. Russo
Senior Medical Advisor, GW Pharmaceuticals, 2235 Wylie Avenue, Missoula, MT 59802, USA
Correspondence to: Ethan B. Russo, M.D.
Senior Medical Advisor, GW Pharmaceuticals
2235 Wylie Avenue
Missoula, MT 59802, USA
VOICE: +1 406-542-0151
FAX: +1 406-542-0158
EMAIL: erusso@montanadsl.net
Submitted: December 1, 2003
Accepted: February 2, 2004
Key words:
cannabis; cannabinoids; medical marijuana; analgesia; migraine;
headache; irritable bowel syndrome; bromyalgia; causalgia;
allodynia; THC; CBD
Neuroendocrinol Lett 2004; 25(1/2):31–39 NEL251204R02 Copyright © Neuroendocrinology Letters www.nel.edu
Abstract
OBJECTIVES
: This study examines the concept of clinical endocannabinoid de-
ciency (CECD), and the prospect that it could underlie the pathophysiology of
migraine, bromyalgia, irritable bowel syndrome, and other functional condi-
tions alleviated by clinical cannabis.
METHODS: Available literature was reviewed, and literature searches pursued
via the National Library of Medicine database and other resources.
RESULTS: Migraine has numerous relationships to endocannabinoid func-
tion. Anandamide (AEA) potentiates 5-HT1A and inhibits 5-HT2A receptors
supporting therapeutic efcacy in acute and preventive migraine treatment.
Cannabinoids also demonstrate dopamine-blocking and anti-inammatory
effects. AEA is tonically active in the periaqueductal gray matter, a migraine
generator. THC modulates glutamatergic neurotransmission via NMDA recep-
tors. Fibromyalgia is now conceived as a central sensitization state with sec-
ondary hyperalgesia. Cannabinoids have similarly demonstrated the ability to
block spinal, peripheral and gastrointestinal mechanisms that promote pain in
headache, bromyalgia, IBS and related disorders. The past and potential clini-
cal utility of cannabis-based medicines in their treatment is discussed, as are
further suggestions for experimental investigation of CECD via CSF examina-
tion and neuro-imaging.
CONCLUSION: Migraine, bromyalgia, IBS and related conditions display
common clinical, biochemical and pathophysiological patterns that suggest an
underlying clinical endocannabinoid deciency that may be suitably treated
with cannabinoid medicines.
R E V I E W A R T I C L E
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Abbreviations
AEA: arachidonylethanolamide, anandamide
2-AG: 2-arachidonylglycerol
CB
1
: cannabinoid 1 receptor
CBD: cannabidiol
CECD: clinical endocannabinoid deciency
CGRP: calcitonin gene-related peptide
CNS: central nervous system
CRP: complex regional pain
ECT: electroconvulsive therapy
FAAH: fatty acid amide hydrolase
fMRI: functional magnetic resonance imaging
5-HT: 5-hydroxytryptamine, serotonin
GI: gastrointestinal
IBS: irritable bowel syndrome
NMDA: N-methyl-d-aspartate
PAG: periaqueductal gray
PET: positron emission tomography
PTSD: post-traumatic stress disorder
RSD: reex sympathetic dystrophy
THC: ∆
9
-tetrahydrocannabinol
TMJ: temporomandibular joint
VR
1
: vanilloid 1 receptor
Introduction
In the initial lines of his 1895 work, Project for a
Scientic Psychology, Sigmund Freud stated [1] (p.
295), “The intention is to furnish a psychology that
shall be a natural science: that is, to represent psy-
chical processes as quantitatively determinate states
of speciable material particles, thus making those
processes perspicuous and free from contradiction.”
Freud was frustrated in this effort, and found that
available science at the twilight of the 19
th
century was
not capable of providing biochemical explanations for
cerebral processes, leading him to pursue psychody-
namic theory alternatively.
At the dawn of the 21
st
century, despite astounding
progress in psychopharmacology, medicine remains
challenged in its attempts to understand and success-
fully treat a large number of recalcitrant syndromes,
noteworthy among them, migraine, bromyalgia, and
irritable bowel syndrome (IBS). For many physicians
these problematic entities suggest a psychosomatic
or “functional” etiology that remains shorthand for
a diagnosis where our biochemical understanding and
therapeutic vigor fall short of the mark.
In the last fteen years, however, the discovery
of the endogenous cannabinoid (endocannabinoid)
system [2] has provided new insights into a neuro-
modulatory scheme that portends to provide better
explanations of, and treatments for, a wide variety of
previously intractable disorders, particularly painful
conditions (reviewed in [3; 4]).
After all, for each neurotransmitter system there
are pathological conditions attributable to its de-
ciency: dementia in Alzheimer disease due to loss of
acetylcholine activity, Parkinsonism due to dopamine
deciency, depression secondary to lowered levels of
serotonin, norepinephrine or other amines, etc. Should
the situation be any different for the endocannabinoid
system, whose receptor density is in fact greater than
many of the others? This article will explore that ques-
tion and propose a concept rst articulated in prior
publications [5; 6], that a clinical endocannabinoid de-
ciency (CECD), whether congenital or acquired may
help to explain the pathophysiology of certain diagnos-
tic pitfalls, especially those characterized by hyperal-
gesia, and thereby provide a basis for their treatment
with cannabinoid medicines.
Mechanisms of action of cannabis and THC have
recently been elucidated with the discovery of canna-
binoid receptors and an endogenous ligand, arachido-
nylethanolamide, nicknamed anandamide, from the
Sanskrit word ananda, or “bliss” [7]. Anandamide
(AEA) inhibits cyclic AMP mediated through G-pro-
tein coupling in target cells, which cluster in nocicep-
tive areas of the CNS [8]. Preliminary tests of its phar-
macological action and behavioral activity support
similarity of AEA to THC [9], and both entities are
partial agonists at the CB
1
receptor. Pertwee [4] has
examined the pharmacology of cannabinoid receptors
and pain in detail.
Methods
Available literature was reviewed, and literature
searches pursued via the National Library of Medicine
database and other Internet resources.
Results
Migraine
Migraine is a public health issue of astounding soci-
etal cost. There are an estimated 23 million sufferers in
the USA [10], with an economic impact of $1.2 to $17.2
billion annually [11]. The neurochemistry of migraine
is among the most complex of any human malady, and
its relation to cannabinoid mechanisms has been ex-
amined previously in brief [12] and in depth [5].
Serotonergic pathways are considered integral to
migraine pathogenesis and treatment. Numerous
points of intersection with cannabinoid mechanisms
are evident: THC inhibits serotonin release from the
platelets of human migraineurs [13]; THC stimulates
5-HT synthesis, inhibits synaptosomal uptake, and
promotes its release [14]; AEA and CB
1
agonists
inhibit rat serotonin type 3 (5-HT
3
) receptors [15] in-
volved in emetic and pain responses. Additionally, AEA
produces an 89% relative potentiation of the 5-HT
1A
receptor response, and a 36% inhibition of the 5-HT
2A
receptor response [16]. Another endocannabinoid, 2-
arachidonylglycerol (2-AG) inhibited 5-HT
2A
by 28%.
Recently, mild but signicant similar activity on 5-
HT
2A
has been demonstrated for cannabidiol [17], and
cannabis terpenoids [18]. Higher concentrations of
anandamide decreased serotonin and ketanserin bind-
ing (the latter being a 5-HT
2A
antagonist) [19]. These
observations support putative efcacy of therapeutic
cannabinoids in acute migraine (agonistic activity at
5-HT
1A
or D) and in its prophylactic treatment (an-
tagonistic activity at 5-HT
2A
) [20].
The importance of dopaminergic mechanisms in
migraine has also been explored [21]. 6-hydroxydo-
pamine, which causes degeneration of catecholamine
Ethan B. Russo
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terminals, blocked THC antinociception [22]. AEA
stimulates nitric oxide formation through inhibition of
presynaptic dopamine release [23]. Dopamine block-
ing and modulatory effects of cannabis and THC have
been demonstrated in studies of Tourette syndrome
[24; 25], and schizophrenia in Germany [26], suggest-
ing that THC may similarly modulate dopaminergic
imbalances in headache.
Inammatory mechanisms affected by cannabis
are legion (reviewed [27–31]. THC and cannabinoids
inhibit prostaglandin E-2 synthesis [32]; smoked can-
nabis reduces platelet aggregation [33]; THC demon-
strated an oral potency as an anti-inammatory 20
times that of aspirin and twice that of hydrocortisone
[34], and cannabidiol (CBD) inhibited both cyclooxy-
genase and lipoxygenase. Similarly, anandamide and
metabolites are substrates for brain lipoxygenase [35].
Opiates, cannabinoids and eicosanoids signal through
common nitric acid coupling [36], while THC blocks
the conversion of arachidonate into metabolites de-
rived by cyclooxygenase activity, and stimulates lipox-
ygenase, promoting down-regulation of inammation.
CNS beta-endorphin levels are depleted during mi-
graine attacks [37], but THC experimentally increases
them [38]. THC additionally regulates substance P
and enkephalin mRNA levels in the basal ganglia
[39]. THC affects an analgesic brainstem circuit in
the rostral ventromedial medulla that interacts with
opiate pathways [40], mediating antinociception after
activation of neurons in the midbrain periaqueductal
grey matter (PAG), a putative migraine generator
area [41], wherein THC and other cannabinoids are
antinociceptive [42]. The PAG is an integral processor
of ascending and descending pain pathways, fear and
anxiety [43]. Additional support is provided by studies
demonstrating tritiated sumatriptan binding in hu-
man PAG [44], and that THC administration elevates
proenkephalin gene expression in the PAG [45]. Most
compelling is data supporting tonic activity of anan-
damide in the PAG with production of analgesia, and
hyperalgesia upon cannabinoid antagonism [46].
Cannabinoids may represent a therapeutic ad-
vantage over opiates, particularly in treatment of
neuropathic pain [47]. Opiates commonly aggravate
migraine or even provoke its appearance [48], as
observed therapeutic doses of morphine failed to al-
leviate acute attack and increased hyperalgesia in
migraineurs during inter-ictal periods.
A trigeminovascular system has long been impli-
cated as integral to the pain, inammation and sec-
ondary vascular effects of migraine, linked through
the NMDA/glutamate system [49]. Cannabinoid
agonists inhibit voltage-gated calcium channels, and
activate potassium channels to produce presynaptic
inhibition of glutamate release [50], without dissocia-
tive effects noted with other NMDA inhibitors, such
as ketamine. Subsequently, THC was shown to modu-
late glutamatergic transmission through a reduction
without blockade [51]. NMDA antagonism was felt
to be effective in eliminating hyperalgesia associated
with migraine [52], as well a “secondary hyperalge-
sia” with exaggerated responses to noxious stimuli in
areas adjacent to the pain. NMDA blockade was rec-
ommended to treat chronic daily headache [53]. This
group also addressed how a genetic predisposition
(“third hyperalgesia”) may lead to a “chronicization”
of migraine through NMDA stimulation [54].
THC and CBD phytocannabinoids also act as
neuroprotective antioxidants against glutamate
neurotoxicity and cell death mediated via NMDA,
AMPA and kainate receptors [55], independently of
cannabinoid receptors, and exceed the antioxidant
potency of vitamins C and E.
Migraine is a complex neurochemical disorder with
myriad effects beyond pain. Its tendency to produce
photophobia and phonophobia, even between discreet
attacks [56], may be considered suggestive of a “sen-
sory hyperalgesia,” as these normally tolerated sensa-
tions take on painful proportions.
The combination of endocannabinoids and their
inactive precursors have been dubbed an entourage
effect [57], and an analogous synergy of phytocan-
nabinoids, cannabis terpenoids and avonoids has also
been suggested and analyzed at some length [58]. The
unique attributes of cannabis to affect serotonergic,
dopaminergic, opioid, anti-inammatory, and NMDA
mechanisms of migraine, both acutely and prophylac-
tically, have rendered it a proposed “ideal drug” for its
treatment [5].
Migraine is a strongly genetic disorder, but similar
symptoms are acquired under conditions of closed
head injury, where the “post-traumatic syndrome”
displays similar symptoms. A protective role of
endocannabinoids in such settings is evident in the
ndings that 2-AG is elevated after experimental brain
injury, and that it plays an important neuroprotective
role [59].
Unfortunately, no organized clinical trials of can-
nabis in migraine have been performed. While docu-
mentation of the use of cannabis for migraine suggests
a 4000 year history, and it was a major indication for
cannabis medicines in Western society between 1842
and 1942 [5], there have been few modern studies be-
yond the “anecdotal” [5; 60–62]. Surveys in California
indicate that of 2480 patients served by the Oakland
Cannabis Buyers’ Club, 127, or 5%, sought cannabis
for treatment of chronic migraines [63]. Success rates
of some 80% with North American strains of canna-
bis have been estimated based on clinical contact [5].
Experience in prophylactic use of Marinol® (synthetic
THC) in some ten patients was disappointing, with
some decrement in frequency and severity of attacks,
but not total remission or “cures” claimed by 19
th
century authors with extracts of Indian hemp [5]. The
difference may well be due to a nearly total dearth of
cannabidiol in North American cannabis strains [64]
(see discussion below), and the observed possibility of
CBD modulation of serotonergic function [17]. More
formal documentation of clinical efcacy would be dis-
tinctly welcome.
Clinical Endocannabinoid Deciency (CECD)
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Fibromyalgia
Fibromyalgia, or myofascial pain syndrome, is
an extremely common but controversial condition,
whose very basis has been questioned, particularly
among neurologists [65]. Even this author must ad-
mit to past prejudice in labeling it a “semi-mythical
pseudo-disease.” Notwithstanding these opinions, the
condition is the most frequent diagnosis in American
rheumatology practices. Bennett has provided an
excellent review [66], emphasizing new insights into
bromyalgia as a condition indicative of “central sen-
sitization” and amplication of somatic nociception.
While no clear chemical or anatomical pathology has
been claried in tender muscle points, these present
a self-sustaining and amplifying inuence on pain
perception in the brain over time, and lead to a con-
comitant disturbances in restful sleep, manifestations
of dysautonomia, and prevalent secondary depression.
Interestingly, the application of standard antidepres-
sant medication to the latter, and pharmacotherapy in
general, provide disappointing results in bromyalgia
treatment. Has a promising therapeutic avenue been
missed?
Returning to the work of Nicolodi and Sicuteri, the
“secondary hyperalgesia” manifested by an increased
response to noxious stimuli in areas adjacent to the
pain is common to migraine and bromyalgia (see be-
low). These authors suggested NMDA blockade as an
approach to pain in defects of serotonergic analgesia in
bromyalgia [67].
Several studies of Richardson and her group pro-
vide key support for a relation of bromyalgia and
similar conditions to a clinical endocannanabinoid
deciency. An initial study [68] demonstrated that
intrathecal injection of SR141716A, a powerful
cannabinoid antagonist/inverse agonist, resulted in
thermal hyperalgesia in mice. This suggests that
the endocannabinoid system regulates nociceptive
thresholds, and that absence of such regulation, or
endocannabinoid hypofunction, underlies hyperal-
gesia and related chronic pain conditions. In a sub-
sequent study [69], oligonucleotides directed against
CB
1
mRNA produced signicant hyperalgesia. Ad-
ditionally, the hyperalgesic effect of SR141716A was
blocked in a dose-dependent manner by co-adminis-
tration of two NMDA receptor antagonists, again sup-
porting tonic activity of the endocannabinoid system
under normal conditions. On this basis, it was sug-
gested that cannabinoid agonists would be applicable
to treatment of chronic pain conditions unresponsive
to opioid analgesics.
Further investigation demonstrated that intrathe-
cal AEA totally blocked carrageenan-induced spinal
thermal hyperalgesia, while having no effect on nor-
mal thermal sensory and antinociceptive thresholds
[70]. Additionally, AEA inhibited K
+
and capsaicin-
evoked calcitonin gene-related peptide (CGRP) re-
lease, and CB
1
receptors were identied in rat sensory
neurons and trigeminal ganglion. On this basis, the
authors recommended cannabinoids for disorders
driven by a primary afferent barrage (e.g., allodynia,
visceral hyperalgesia, temporomandibular joint pain
(TMJ), and reex sympathetic dystrophy (RSD)), and
that such treatment could be effective a sub-psychoac-
tive dosages.
Another study examined peripheral mechanisms
[71], wherein AEA acted on CB
1
to reduce hyperal-
gesia and inammation via inhibition of CGRP neu-
rosecretion in capsaicin activated nerve terminals.
This is akin to mechanisms of “sterile inammation”
observed centrally in migraine, where CGRP is felt
to be an important mediator [5]. Overall the results
supported the notion that endocannabinoids modu-
late neurogenic inammation through inhibition of
peripheral terminal neurosecretion in capsaicin-sen-
sitive bers. AEA demonstrated anti-edema effects
in addition to anti-hyperalgesia. Similar implications
were provided by another study [72], in which WIN
55,212–2, a powerful CB
1
agonist, blocked capsaicin-
induced hyperalgesia in rat paws. Once more, the ben-
et occurred at a dosage that did not produce analgesia
or motor impairment, suggesting therapeutic benet
of cannabinoids without adverse effects. Similarly, lo-
cal THC administration was evaluated in capsaicin-in-
duced pain in rhesus monkeys [73], where, once more,
pain was effectively reduced at low dosage, and was
blocked by a CB
1
antagonist.
Another concept that is important to understand-
ing of bromyalgia is “wind-up,” a central sensitiza-
tion of posterior horn neurons in pain pathways that
occurs secondarily to tonic impulses form nociceptive
afferent C bers dependent on NMDA and substance
P synaptic mechanisms in the spinal cord [74]. Simi-
lar mechanisms were implicated in TMJ dysfunction
and RSD/CRP syndromes. The authors felt that some
unknown peripheral tonic mechanism maintains
allodynia, hyperalgesia, central sensitization and en-
hanced wind-up. Unfortunately, an obvious explana-
tion was overlooked. In a previous publication [75],
it was demonstrated that of wind-up was decreased in
dose-dependent fashion by WIN 55,212 in spinal wide
dynamic range and nociceptive-specic neurons. Thus,
cannabinoids were able to suppress facilitation of spi-
nal responses after repetitive noxious stimuli without
impairment of non-nociceptive functions.
On a practical level, once more there have been no
formal clinical trials of cannabis or THC in treatment
of bromyalgia. However, 21 California patients listed
bromyalgia and 11 myofascial pain (1.3% of a clini-
cal population of 2480 subjects) as primary diagnoses
leading to their usage of clinical cannabis [63]. Anec-
dotal reports to this author and other clinicians sup-
port unique efcacy of cannabis beyond conventional
pharmacotherapy for alleviation of pain, dysphoria
and sleep disturbances.
Irritable Bowel Syndrome (IBS)
IBS is another difcult clinical syndrome for pa-
tients and their physicians. It is characterized by
uctuating symptoms of gastrointestinal pain, spasm,
distention, and varying degrees of constipation or es-
pecially diarrhea. These may be triggered by infection,
Ethan B. Russo
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but dietary indiscretions also gure prominently in
discrete attacks. Although many clinicians regard it as
a “diagnostic wastebasket,” irritable bowel syndrome
represents the most frequent referral diagnosis for
American gastroenterologists. Once more, a wide va-
riety of treatments including atropinic agents, antide-
pressants and others affecting a myriad of neurotrans-
mitter systems are prescribed, often with inadequate
clinical benets.
That endocannabinoids are important in GI func-
tion was powerfully underlined by the fact that 2-
arachidonylglycerol (2-AG) was rst isolated in canine
gut [76].
In a recent review [77], the concept of “functional”
bowel disorders as disturbances displaying “visceral
hypersensitivity” was emphasized, involving a veri-
table symphony of neuroactive and pro-inammatory
modulators. In the susceptible subject, these lead to
gastrointestinal allodynia and hyperalgesia to stimuli
that would not discomt the unaffected individual.
The role of vanilloid mechanisms in IBS was also ex-
plored, and it is worth emphasizing that anandamide
is an endogenous agonist at VR
1
receptors, as is the
phytocannabinoid cannabidiol (CBD) [78]. Repetitive
VR
1
stimulation rapidly produces a sensory neuron
refractory state that would be a clinical advantage in
treatment of visceral hypersensitivity.
Pertwee has examined the relationship of cannabi-
noids to gastrointestinal function in depth [79]. To
summarize: The enteric nervous systems of mammals
express CB
1
and stimulation depresses gastrointesti-
nal motility, especially through inhibition of contrac-
tile neurotransmitter release. Observed effects include
delayed gastric emptying, some decrease in peptic acid
production, and slowed enteric motility, inhibition
of stimulated acetylcholine release, peristalsis, and
both cholinergic and non-adrenergic non-cholinergic
(NANC) contractions of smooth muscle, whether cir-
cular or longitudinal. These effects are mediated at the
brain level as well as in the GI tract (This supports a
chestnut frequently invoked by this author, ‘The brain
and the gut speak the same language.”). These effects
are opposed by CB
1
antagonists (e.g., SR141716A).
This would strongly support the notion that GI motil-
ity is under tonic control of the endocannabinoid sys-
tem. The latter concept was reinforced by additional
investigation from the same laboratory [80], in which
it was demonstrated that the virtually all of the immu-
noreactive myenteric neurons in the ganglia of rat and
guinea pig expressed CB
1
receptors, and that there was
a close correlation of such receptors to bers labeled
for synaptic protein, suggesting a fundamental role
in neurotransmitter release. Additionally, it has been
shown that chronic intestinal inammation results in
an up-regulation or sensitization of cannabinoid recep-
tors [81]. CBD has little effect on intestinal motility on
its own, but synergizes the effect of THC in slowing
transit of a charcoal meal when used in concert [82].
In the basis of available data, Di Carlo and Izzo
recommended the application of cannabinoid drugs
in treatment of IBS in humans [83]. To date, those
studies have not eventuated, but cannabis has a long
history in treating cholera, intestinal colic and related
disorders (reviewed in [84]), and cannabis gures
prominently in IBS treatment in testimonials on the
Internet. Though anecdotal, reports suggest unique
efcacy of symptomatic relief at cannabis dosages that
do not impair activities of daily living. In comparison,
recent trends in pharmacotherapy provide interest-
ing contrasts. Alosetron, a 5-HT
3
receptor antagonist
marketed for females with diarrhea-predominant IBS
produces only a 12–17% therapeutic gain [85], and
was temporarily removed from the American market
due to fatal cases of ischemic colitis with attendant
obstipation. Tegaserod, a 5-HT
4
receptor agonist
marketed to women with constipation-predominant
IBS, is reportedly well tolerated, but provides only a
5–15% improvement over placebo [85]. This “push-
pull” dichotomy of serotonergic function in IBS is
strongly suggestive that such efforts are barking up
the wrong neurotransmitter tree. Rational analysis
suggests that endocannabinoids may well be the more
likely therapeutic neuromodulatory target, and that
phytocannabinoid treatment might represent a more
efcacious and safer therapeutic approach. In particu-
larly severe IBS cases, the employment of a foaming
rectal preparation of a whole cannabis extract might
be considered.
Comorbidities of Migraine, Fibromyalgia
and Irritable Bowel Syndrome
Further examination of pertinent literature sup-
ports that there are very interesting relationships
between migraine, bromyalgia and IBS. Recently,
a syndrome of cutaneous allodynia associated with
migraine has been reported [86], and experimen-
tally, repetitive noxious stimulation of the skin in
migraineurs between attacks facilitates pain percep-
tion [87]. Nicolodi, Sicuteri et al. similarly noted a
decreased pain threshold in migraineurs tested with
over-distension of upper extremity veins, but not mere
pressure from a sphygmomanometer cuff [88], merit-
ing a label for migraine as a “visceral systemic sensory
disorder.” The same team noted a baseline fragility
of serotonergic systems in migraine and bromyalgia
[89], plus the co-occurrence of primary headache in
97% of 201 bromyalgia patients. In a later study
[67], they supported the concept that both disorders
represented a failure of serotonergic analgesia and
NMDA-mediated neuronal plasticity. Other observa-
tions included the induction of bromyalgic symptoms
by the drug fenclonine in migraineurs but not others,
and the production of migraine de novo in bromyalgia
patients without prior history after administration
of nitroglycerine 0.6 mg sublingually. Similarly, an
American group [90] examined 101 patients with the
transformed migraine form of chronic daily headache,
and were able to diagnose 35.6% as having comorbid
bromyalgia. Similarly, a high lifetime prevalence of
migraine, IBS, depression and panic disorder were
observed in 33 women meeting American College of
Rheumatology criteria of bromyalgia [91].
Clinical Endocannabinoid Deciency (CECD)
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Sperber et al. examined separate groups of IBS and
bromyalgia patients [92]. Of the IBS cohort, 31.6%
had bromyalgia with signicant numbers of tender
muscle points compared to controls. Similarly, 32% of
bromyalgia patients met diagnostic criteria of IBS. In
addition to these correlations, Bennett added irritable
bladder syndrome to the comorbidities of bromyalgia
[66], supporting a concomitant visceral hyperalgesia
[93; 94] in a condition where cannabis extracts have
already proven efcacious [95].
Most recently, in an experimental protocol, it was
demonstrated that IBS patients displayed cutaneous
hyperalgesia that was suppressed by temporary rectal
anesthesia with lidocaine [96], indicating central sen-
sitization.
Broadening the Concept of Clinical
Endocannabinoid Deciency
One may quickly see that certain patients display
symptoms of all three disorders, or additional ones
considered “functional.” With accrual of sufcient
numbers of complaints lacking objective medical sup-
port, one assigns the label of somatization disorder.
Given the above data, however, one might reasonably
ask three questions in such contexts: 1) Are there as
yet unelucidated biochemical explanations for these
disorders? 2) Might endocannabinoid deciency ex-
plain their pathophysiology? 3) Are the symptoms al-
leviated by clinical cannabis?
Globus hystericus and similar symptoms are
frequently relegated to the psychogenic realm, but
as a spasmodic disorder, it may well represent an
endocannabinoid deciency (CECD), as muscle tone
(and tremor associated with demyelination) have been
demonstrated to be under tonic endocannabinoid con-
trol in experimental animals [97]. Cannabis extracts
have already proven efcacious in treatment of spas-
ticity [98; 99].
Similarly, premature ejaculation in men is conven-
tionally perceived as “psychological.” This seems less
tenable, when anecdotes support that cannabis pro-
longs latency, and proof is apparent in the dose respon-
sive delay in ejaculation in rats noted in experiments
with HU 210, a powerful CB
1
agonist [100].
A more obvious set of correlating conditions would
be those of causalgia, allodynia and phantom limb
pain, where application of cannabis based medicine
extracts has already proven medically effective [99;
101]. Perhaps it will be demonstrable in the future
that such conditions are associated with focal or spinal
CECD states.
It has long been known that cannabinoids lower
intraocular pressure in glaucoma (reviewed [102]),
but only recently noted that that the mechanism is
under tonic endocannabinoid control. Glaucoma also
represents a vascular retinopathy for which cannabis
may be neuroprotective. Perhaps an endocannabinoid
deciency is operative here as well.
Cannabis has had numerous historical applications
to obstetrics and gynecology (reviewed [103]). This
suggests usage of cannabinoid treatment in spasmodic
dysmenorrhea, hyperemesis gravidarum, and regula-
tion of the uterine milieu in fertilization and unex-
plained fetal wastage, where endocannabinoid mecha-
nisms have been demonstrated or implicated. Further
investigation may shed light on whether dysregulation
of the system underlies their pathophysiology.
In the pediatric realm, the entity of infantile colic
has remained enigmatic. This disturbing anomaly is as-
sociated with apparent visceral sensitivity and distinct
dysphoria, and is frequently medically recalcitrant to
even desperate treatment measures with medications
with serious adverse effect proles. This author posits
this to be another developmental endocannabinoid
deciency state that is likely amenable to phytocan-
nabinoid treatment.
Endocannabinoid mechanisms also regulate
bronchial function [104], and therapeutic efcacy in
asthma treatment with cannabis preparations has
been long known [105]. Based on similar analyses of
the multi-organ involvement of cystic brosis [106],
Fride has proposed endocannabinoid deciencies as
underlying the pathophysiology of that disorder, and
its treatment with phytocannabinoids.
In the psychiatric realm, bipolar disorder has been
therapeutically recalcitrant to high dose antidepres-
sants, but anecdotal data support cannabis efcacy
[107]. Whether endocannabinoid tone is too low in
the disorder would be conjectural at this time, but in
the instance of post-traumatic stress disorder (PTSD),
such a foundation seems likely, as endocannabinoids
have been demonstrated as essential to the extinction
of aversive memories in experimental animals [108].
Recent work by Wallace et al. has also demon-
strated that convulsive thresholds are also under
endocannabinoid control [109; 110], and that THC
prevents 100% of subsequent seizures, far in excess
of the capabilities of phenobarbital and phenytoin.
Affected rats demonstrated both acute increases in
endocannabinoid production and a long-term up-regu-
lation of CB
1
production as apparent compensatory ef-
fects counteracting glutamate excitotoxicity. Based on
this, one might conjecture that similar changes accrue
when seizures are employed therapeutically as electro-
convulsive therapy (ECT), in treatment of intractable
depression. It seems that the resultant memory loss
and prolonged improvement in mood may well be at-
tributable to an increase in endocannabinoid levels
rectifying their previous inadequacy.
Recent theory on depression suggests that mere
deciencies of serotonin and norepinephrine may be
insufcient explanations of the disorder, but rather,
innate neuroplasticity is inherently impaired and
requires specic treatment [111]. Cannabinoids
certainly seem to enhance that plasticity with their
neuroprotective abilities [112; 113], and should be fur-
ther explored therapeutically.
The apoptotic and anti-angiogenic properties of
endo- and phytocannabinoids in various cancers (re-
viewed [114; 115]) raise the hypothesis that certain
people who are especially susceptible to malignancy
may be endocannabinoid decient.
Ethan B. Russo
36
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37
Neuroendocrinology Letters Nos.1/2 Feb-Apr Vol.25, 2004 Copyright © Neuroendocrinology Letters ISSN 0172–780X www.nel.edu
Conclusions
Clinical Endocannabinoid Deciency:
Is It a Provable Concept?
The preceding material has pertained to conjectural
and experimental evidence of a conceptual alternative
biochemical explanation for certain disease manifes-
tations, but one must ask how these would obtain?
Baker et al. have described how endocannabinoids
may demonstrate an impairment threshold if too high,
and a range of normal function below which a decit
threshold may be crossed [112]. Syndromes of CECD
may be congenital or acquired. In the former case, one
could posit that genetically-susceptible individuals
might produce inadequate endocannabinoids, or that
their degradation is too rapid. The same conditions
might be acquired in injury or infection. Unfortu-
nately, the regulation of endocannabinoid synthesis
and degradation are far from fully elucidated (re-
viewed [116]). While a single enzyme, anandamide
synthase, catalyzes AEA production, its degrada-
tion by fatty acid amidohydrolase (FAAH), is shared
with many substrates. To complicate matters, an
endocannabinoid with antagonistic properties at CB
1
called virodhamine (virodha, Sanskrit for “opposi-
tion”) has recently been discovered [117]. Further re-
search may shed light on these relationships.
In the meantime, a clinical agent that modies
endocannabinoid function will soon be clinically avail-
able in the form of cannabidiol. Recent research has
demonstrated that although THC does not share VR
1
agonistic activity with AEA, CBD does so to a similar
degree as capsaicin [78]. What is more, CBD inhibits
uptake of the endocannabinoid anandamide (AEA),
and weakly inhibits its hydrolysis. The presence of
this component in available cannabis based medicine
extracts portends to vastly extend the clinical appli-
cations and therapeutic efcacy of this re-emerging
modality [118–120].
It is highly likely that additional regulatory roles
for endocannabinoids will be discovered for this neuro-
and immunomodulatory system. Some simple human
experiments may be valuable, such as cerebrospinal
uid assay of AEA and 2-AG before and after ECT
treatment. It is likely in the future that positron emis-
sion tomography (PET) or functional magnetic reso-
nance imaging (fMRI) for cannabinoid ligands may
clarify these concepts.
This article has examined the inter-relationships
of three clinical syndromes and biochemical basis in
endocannabinoid function, as well as reecting on
other conditions that may display similar correlations.
Only time and the scientic method will ascertain
whether a new paradigm is applicable to human physi-
ology and treatment of its derangements. Our insight
into these possibilities is dependent on the contribu-
tion of one unique healing plant; for clinical cannabis
has become a therapeutic compass to what modern
medicine fails to cure.
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Clinical Endocannabinoid Deciency (CECD)
