Medicinal cannabis can be used for various conditions. Especially if traditional medicines do not help patients sufficiently or if the side-effects are too severe.
In general, up-to-date research indicates that medicinal cannabis does not cure diseases or disorders, but it can relieve symptoms associated with them or halt progression of a disease. Based on randomised, double-blind, controlled clinical studies, it has been confirmed cannabinoids exhibit therapeutic potential in the case of:
Outside the care of their doctors, patients self-medicate with cannabis for a wide range of medical conditions. Based on the available scientific evidence, further attention should be focused on other potential uses of medicinal cannabis. This includes the treatment of:
- Inflammatory bowel diseases
- Insomnia/sleeping disorders
- Parkinson’s disease
- Psychiatric disorders
Alongside these conditions, cannabinoids show promising results in the symptomatic treatment of hyperactivity, anxiety disorders and allergies.
Treatment: Mainly pain associated with the nervous system, for example pain caused by damaged nerves, phantom pain, facial neuralgia, or shingles.
Severe chronic pain seems to be the major reason for which patients use cannabis medicinally. There are many types of pain, and cannabis does not influence each pain type identically. The therapeutic effects of cannabinoids seem to be most pronounced in neuropathic pain – the pain originating from injury or disease that affects the sensory nerves. A prime example of this disease type is multiple sclerosis (MS), where the patients’ nerves are attacked by their own immune system.
Another example is fibromyalgia, where the nerves become hypersensitive and even a mild touch is perceived as painful. Cannabis may represent an alternative treatment for patients with fibromyalgia who are unresponsive to conventional therapy. However, its application may be limited by the incidence of nonserious adverse events.
In contrast, studies measuring the effects on acute pain (e.g. postoperative pain) often show no beneficial effects of cannabis. Most likely, this difference is related to the role endocannabinoids play in both types of pain. However, the mechanism behind this difference is not yet fully understood.
Studies exploring patient therapeutic preferences indicate that for severe pain the majority of side-effects from cannabinoids are better tolerated than those from prolonged use of high doses of opioid medications. Chronic neuropathic pain is a common and difficult-to-treat symptom with limited treatment options. As a consequence, even modest therapeutic effects of cannabinoids may be relevant for suffering patients.
Because chronic pain is difficult to treat with any single medicine, cannabinoids have often been studied in combination with other therapeutics, including strong opioids such as morphine. It was found that cannabinoids and opioids work together with a strong combined effect. This effect is called ‘synergy’. As a result, the addition of cannabinoids can often result in a lowering of the opioid dose in a patient’s daily drug regimen. Dual therapies have been seen to reduce the unwanted mild to severe side effects of opioids, for example, nausea and vomiting, tolerance, sedation and respiratory depression.
Treatment: Pain and muscle spasms or cramps associated with multiple sclerosis (MS) or spinal cord damage.
Together with chronic pain, multiple sclerosis is the other medical condition in which long-term effects of cannabinoids have been studied extensively (mainly in the form of the pharmaceutical product Sativex®). The studies show patients do not develop a tolerance for the medicinal effects, nor do they increase their doses over time to achieve the same therapeutic result. Although the medical evidence supporting cannabis use for MS is still limited, it is important to note the same is true for most conventional MS medications.
Numerous patients worldwide currently use cannabis and cannabinoids to alleviate pain, muscle spasms, or cramps associated with MS or spinal cord damage. Indeed, the majority of clinical trials with cannabinoid-based medicines have focused on MS. Standard therapy often provides inadequate relief and can be limited by medication side effects. Consequently, patients suffering from MS have historically experimented with alternative therapies, including cannabis, to improve their quality of life. Nowadays, scientific evidence exists supporting the beneficial effects of cannabinoids on disease-related pain, bladder symptoms, tremor, and spasticity. Additionally, sleep improves significantly by using cannabinoids, resulting in both deeper and longer sleep.
Nausea, vomiting and appetite
Treatment: Nausea, vomiting and appetite associated with chemotherapy or radiotherapy used in the treatment of cancer. Appetite and weight loss and debilitation due to hepatitis C, cancer or HIV infection and AIDS.
Cannabis can have strong effects on nausea and vomiting resulting from cancer chemotherapy or radiotherapy treatment, hepatitis C, HIV infection or AIDS. Since 1986, synthetic THC (as Marinol®) has been approved by the US Food and Drug Administration (FDA) as an appetite stimulant in the case of anorexia associated with weight loss in patients with HIV/AIDS. Marinol® has also been approved as an antiemetic for cancer patients undergoing chemotherapy. Supporting studies suggest that the addition of THC directly before and after chemotherapy offer more benefit than conventional antiemetic medications alone.
Cannabis has been shown to stimulate appetite, described as a strong desire for foods with high fat or sugar content. For these patients, a high caloric intake may contribute to weight gain and to the absorption of nutrients, often crucial in combating medical conditions such as AIDS-related wasting syndrome.
Although other drugs are available to treat nausea, vomiting, or reduced appetite, the combined effect of cannabis on all these symptoms at once makes it a unique option for contributing to improving a patient’s quality of life. For patients suffering from nausea or vomiting, often oral medications are inconvenient. For these patients, administration via inhalation – using a vaporization medical device – reduces the burden of oral medication and achieves therapeutic levels rapidly.
Gilles de la Tourette syndrome
Treatment: Inability to control the making of repeated, quick movements or sounds.
Tourette syndrome is a neuropsychiatric disorder, characterised by physical (motor) and vocal (phonic) tics. Anecdotal reports provide some evidence that cannabis is effective not only in the suppression of such tics, but also in the treatment of associated psychiatric disorders such as obsessive-compulsive disorder. Clinical trials investigating the effect of (pure) THC in the treatment of Tourette syndrome showed a significant tic reduction without causing significant adverse effects. Because the highly visible tics have an enormous impact on Tourette patients’ social lives, even a small effect of cannabis could be considered relevant. THC may, therefore, be a promising treatment of Tourette syndrome in adult patients, when first-line treatments failed to reduce the tics.
Treatment: Uncontrolled eye pressure with therapy-resistant glaucoma.
In glaucoma patients, a progressive increase of pressure inside the eye causes a gradual loss of vision, resulting in total blindness if untreated. Studies in the 1970s showed cannabis, when inhaled or eaten, effectively lowers eye pressure as much as standard medications.
Although currently many treatment options are available, glaucoma is still one of the leading causes of irreversible blindness worldwide. Cannabis may be a promising treatment when conventional treatments do not produce the desired effects. However, the duration of the pressure-lowering effect is typically in the range of several hours. Therefore, cannabis medicine would require dosing at regular intervals.
The relationship between cannabis and anxiety is complex. In terms of acute effects, on one hand administering high doses of THC is likely to increase the feeling of anxiety. On the other hand, some research suggests that CBD reduces anxiety. Moreover, administering THC combined with CBD has been shown to decrease the anxiety-inducing effects of THC. Despite that, there is insufficient clinical evidence available to determine whether the effects of THC and CBD on anxiety last in the long-term. Specifically, aside of some limited clinical data on the acute effects of both cannabinoids, it is not clear if THC worsens the course and treatment of anxiety disorders. Conversely, there is no sound clinical data on the beneficial long-term effects of CBD on anxiety disorders. As such, although some of the currently available evidence provides hope that CBD could be used as an effective treatment for anxiety, more clinical research is needed to determine whether that is the case.
Cannabinoids exert palliative effects in cancer patients by reducing nausea, vomiting and pain, by stimulating appetite, and by improving the quality of sleep. However, laboratory studies in animals and isolated cancer cells have shown cannabinoids to be capable, under some conditions, of inhibiting the development of cancer cells in multiple ways.
As a result of such exciting findings, a growing number of non-scientific accounts have appeared on the internet claiming cannabis to be a cure for cancer. Nevertheless, in spite of on-going research, there is currently no solid evidence from clinical trials to support such claims.
It should be noted, however, that the potential effects of terpenes on cancer, either alone or in combination with cannabinoids, are yet to be addressed in laboratory studies. Indeed, the combined effects of cannabinoids and terpenes are often claimed to be the major difference between ‘holistic’ herbal preparations of cannabis and pharmaceutical products based on single cannabinoids. However, the exact nature of the effects of cannabinoid-terpene combinations has not yet been studied.
Moreover, extraction methods and/or administration forms used by self-medicating patients often differ from those used in laboratory or hospital studies. Because of this gap between real-life experiences and clinical research, the curative potential of herbal cannabis preparations for the treatment of different cancer types remains unclear.
Although epilepsy may be well-controlled by existing medications, a significant number of people with epilepsy do not have adequate control of their seizures. Although surgery may be considered for difficult cases, this is a delicate, complicated operation with great risk to a patient’s brain. Therefore, in treatment-resistant patients, the use of cannabis may seem as a viable alternative. As early as in 1979, studies on rats confirmed the anticonvulsant effects of (pure) CBD. In various subsequent animal and (small-scale) human studies, CBD was able to reduce the frequency and severity of seizures. Combined with an absence of psychoactive effects, these results show the potential of CBD as a therapeutic candidate for human epilepsy.
Cannabis is commonly used for sleeping disorders and the available scientific evidence suggests that both THC and CBD can modulate sleep. Nevertheless, as in the case of many other conditions, there are only a few clinical trials on the topic that do not allow for making reliable conclusions. As such, it is difficult to define the specific effects of THC and CBD on sleep and their therapeutic potential in sleep disorders. Although more clinical research is needed on the topic, it is also important to keep in mind that many patients reliably self-report beneficial effects of both THC and CBD on their sleep patterns.
Inflammatory bowel diseases
Currently evidence is accumulating suggesting that cannabinoids can have beneficial effects on inflammatory bowel diseases (IBDs), such as Crohn’s disease and ulcerative colitis. Data obtained from animal studies suggests a homeostatic (regulative) role of the endocannabinoid system in the gut and indicates that manipulating the endocannabinoid system can influence gastrointestinal motility and have an anti-diarrheal effect. However, findings from human studies point to a more complex picture. Specifically, on one hand research has shown that smoking cannabis may increase the appetite and weight of IBD patients, decrease disease activity and reduce the need for other medications. On the other hand, human studies have also shown that the effects of cannabinoids on disease activity may not be as potent as expected, especially in the case of orally administered CBD. In addition, the beneficial effects on IBDs seem to be only symptomatic – no anti-inflammatory effect has been confirmed so far. More controlled clinical studies with different methods of administration are required to better understand the role of cannabinoids in IBDs.
Animal research demonstrates that cannabinoids may have neuroprotective effects in case of Parkinson’s disease (PD) and improve motor symptoms associated with the disease and long-term levodopa treatment. In case of human studies, the evidence is mixed. Some research failed to show any beneficial effects of orally administered cannabinoids (both natural and synthetic) on PD motor symptoms or those induced by levodopa treatment. Conversely, observational studies with smoked cannabis suggest that cannabinoids may improve motor symptoms, such as tremor and rigidity, reduce pain and enhance sleep of PD patients. Moreover, although CBD has not been shown to influence PD symptoms, it has been suggested that it can increase the quality of life of patients. In any case, more controlled clinical research is needed to see to what extent cannabinoids can be applied in the treatment of PD.
Another upcoming, but only partially understood, application of cannabinoids is in the treatment of psychiatric disorders such as schizophrenia, anxiety and bipolar disorder. Although long-term consumption of high doses of THC is a potential risk factor for the development of mental illnesses, other cannabinoids seem to have the reverse effect. In particular, the non-psychoactive cannabinoid CBD has shown potential in the treatment of anxiety and different types of psychosis, like schizophrenia. In a study using pure CBD, it was found to have substantial antipsychotic properties in acute schizophrenia, with an efficacy comparable to the standard drugs. Currently, high CBD cannabis varieties are being developed to respond to the increasing demand for these substances.
The clinical data on the effectiveness of cannabinoids in treating rheumatic diseases is very limited and not consistent, despite many patients treating their symptoms with success. Current evidence suggests that cannabinoids may induce beneficial effects on sleep and pain relief in rheumatic patients. However, the low quality of the available data does not allow to make strong recommendations in this regard.