Ingestion of a THC-Rich Cannabis Oil in People with Fibromyalgia : A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

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To determine the benefit of a tetrahydrocannabinol (THC)-rich cannabis oil on symptoms and quality of life of fibromyalgia patients.


A double-blind, randomized, placebo-controlled clinical trial was conducted for eight weeks to determine the benefit of a THC-rich cannabis oil (24.44 mg/mL of THC and 0.51 mg/mL of cannabidiol [CBD]) on symptoms and quality of life of 17 women with fibromyalgia, residents of a neighborhood with a low socioeconomic profile and a high incidence of violence in the city of Florianopolis, Brazil. The initial dose was one drop (∼1.22 mg of THC and 0.02 mg of CBD) a day with subsequent increases according to symptoms. The Fibromyalgia Impact Questionnaire (FIQ) was applied at pre- and postintervention moments and in five visits over eight weeks.


There were no significant differences on baseline FIQ score between groups. However, after the intervention, the cannabis group presented a significant decrease in FIQ score in comparison with the placebo group (P = 0.005) and in comparison with cannabis group baseline score. (P < 0.001). Analyzing isolated items on the FIQ, the cannabis group presented significant improvement on the “feel good,” “pain,” “do work,” and “fatigue” scores. The placebo group presented significant improvement on the “depression” score after intervention. There were no intolerable adverse effects.


Phytocannabinoids can be a low-cost and well-tolerated therapy to reduce symptoms and increase the quality of life of patients with fibromyalgia. Future studies are still needed to assess long-term benefits, and studies with different varieties of cannabinoids associated with a washout period must be done to enhance our knowledge of cannabis action in this health condition.


Fibromyalgia (FM) is one of the most common chronic pain syndromes, characterized by musculoskeletal pain, extreme fatigue, and sleep and/or mood disorders. It may have a great physical and psychological impact on patients’ lives, preventing work and daily activities. The pathophysiology is mostly unknown, and FM’s etiology involves environmental and genetic factors [1]. The disease affects more women than men, and the Brazilian Rheumatology Association calculates its prevalence in the Brazilian population at about 3%, mostly in women between 30 and 55 years old [2].

Treatment of the condition is based on symptom relief; nevertheless, modest results are obtained with current medications; however, the adverse effects of drugs often hinder patient adherence. In general, poor well-being and quality of life are common [3].

The cannabis plant has been used in pain treatment for centuries; in the last decades, however, its use has been withdrawn from traditional medicine due to legal prohibitions [4]. Scientific studies on the plant’s therapeutic effects have been produced over the last 50 years, and in 2017 the National Academy of Science, Engineering and Medicine concluded, after article reviews, that cannabis use for pain treatment is supported by well-controlled clinical trials, with substantial evidence of its effects in the treatment of chronic pain in adults [5]. Presently, many countries have been reformulating their laws recognizing the medicinal character of this plant.

Cannabis flowers contain over 100 types of phytocannabinoids, chemical compounds that interact with the cannabinoid receptors present in our bodies. The most prevalent and better known are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is found in greater quantity in drug-type cannabis chemovars and is responsible for its popular psychoactive effects: euphoria, lightheadedness, and coordination and recent memory impairment. Beneficial effects are seen on pain control, nausea, anxiety, insomnia, anorexia, and spasticity. CBD presents anti-epileptic, analgesic, anxiolytic, and sedative effects with fewer psychoactive effects. Both phytocannabinoids have anti-inflammatory effects, which seems to be greater when both THC and CBD act together [6].

There are two well-characterized endocannabinoid receptors on animals: CB1 and CB2; CB1 is mostly found in the central nervous system, while CB2 is found in many tissues and organs, especially those with immune-related activities [3]. There is also growing evidence that support the existence of additional receptors for cannabinoids (non-CB1/CB2). This set of receptors, along with endocannabinoid substances (2-arachidonoylglycerol and anandamide) and the associated biochemical apparatus, composes the endocannabinoid system [4]. This system has multiple functions that keep balance in our bodies, including pain and stress modulation, suggesting that its manipulation may be a potential therapeutic focus in FM care.

Considering the far-reaching damage caused by FM and the effect it can have on individuals, their families, communities, and the public health system, it seems necessary to study alternative, low-cost, and well-tolerated therapies that help patients to regain their well-being and quality of life. The present study aims to evaluate the impact that cannabis oil—a THC-rich whole plant extract—can have on symptoms and quality of life of individuals afflicted by FM.


Study Design

A randomized, double-blind, placebo-controlled clinical trial performed with patients of a community Health Center in Florianopolis, Brazil. Data were collected from September to November of 2019.


Users of Monte Cristo Health Center with fibromyalgia or chronic spread pain were recruited by family health teams to participate. Twenty people attended a pre-evaluation meeting with the researcher and signed a written informed consent form that enabled access to their medical records. Diagnosis of fibromyalgia was confirmed at this meeting using American College of Rheumatology (ACR) 2010 criteria [7, 8]. Inclusion criteria were FM diagnosis (ACR 2010 criteria), age over 18 years, presence of moderate to severe symptoms (presenting functional limitation in everyday activities) despite therapies in use, at least one medical or nursing consultation at the Health Center in the last year. Exclusion criteria were decompensated organic comorbidities and/or risk of psychiatric conditions (schizophrenia, psychosis, severe personality disorder, current suicidal ideation), another well-defined cause of chronic pain, current pregnancy/lactation, moderate or severe cognitive impairment, and history of cannabinoid sensitivity.

Randomization and Masking

Participants were randomly assigned through a computer randomization program to two groups, cannabis or placebo, with the help of an external collaborator. This same person was not involved in the rest of the trial and kept allocation information in sealed opaque envelopes until the end of the intervention. The cannabis group received a 30-mL green glass dropper bottle containing cannabis oil (olive oil extraction) of the White Widow [9] variety, at a 24.44-mg/mL concentration of THC and 0.51 mg/mL of CBD—at a proportion of ∼48/1 THC/CBD, among small quantities of other cannabinoids such as cannabigerol, tetrahydrocannabivarin, cannabinol, and cannabicromen. The material was not analyzed for terpenoid profile, although the chosen variety of cannabis is recognized for its terpenoids: myrcene, caryophyllene, and pinene [9]. The product—not standardized—was provided in partnership with the Brazilian Association of Medical Cannabis Patients (AMA+ME). The placebo group received an identical bottle with olive oil inside. Edible brown dye was used to soften differences between liquids. Participants were informed about the possibility of being placed into the placebo group. They were evaluated during the study with prescheduled individual appointments to reduce information exchange at the Monte Cristo Health Center. The main researcher made all the evaluations while blinded. Data analysis was conducted after the end of the intervention.

Procedures and Outcome

The initial dose in both groups was one drop (∼1.2 mg of THC and 0.02 mg of CBD) a day sublingually. Participants in both groups were seen at baseline and every 10 days for eight weeks, and dose increases respected the maximum of one drop for each evaluation moment. At each visit, patients filled out the Fibromyalgia Impact Questionnaire (FIQ), a validated self-administered test that evaluates physical function, work status, well-being, and associated physical and mental symptoms in FM patients [10]. The FIQ is composed of 10 items (“physical function,” “feel good,” “work missed,” “job ability,” “pain,” “fatigue,” “morning tiredness,” “stiffness,” “anxiety,” and “depression”), each with a maximum possible score of 10. Total scores range from 0 to 100, and higher scores mean greater impact on a patient’s quality of life [11]. Clinical and adverse effects were also assessed during each visit to determine change or maintenance of therapy dosage.

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Auteur: Philippe Sérié

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