The idea that hemp can be used in the treatment of many diseases has existed for a long time, as it contains phytocannabinoids, terpenes and many other effective compounds not detailed here. Scientific studies on this subject have increased significantly, especially in the last 5 years. Below are data on the healing effect of cannabis on various diseases or symptoms.
Alzheimer’s
The endocannabinoid system is thought to be one of the target mechanisms in age-related neurodegenerative diseases such as Alzheimer’s. In vivo and in vitro preclinical experiments have shown that cannabinoids reduce ß-amyloid toxicity and have a neuroprotective effect. In the study conducted by Suliman et al. in 2018, it was found that low dose Δ9-THC triggered significant neurogenesis in the hippocampus of old rats. In vitro experiments have shown that THC regulates mitochondrial activities, and therefore it has been stated that THC may slow down the prognosis of Alzheimer’s disease. Δ9-THC has also been found to reduce intraneuronal β-amyloid accumulation and have an anti-inflammatory effect. Inflammation in the brain is one of the key mechanisms in the development of neurodegenerative diseases such as Alzheimer’s. For this reason, it is predicted that selective CB2 agonists, in addition to both CB1 and CB2 receptor agonists such as Δ9-THC, can suppress neuroinflammation and oxidative stress damage and improve decreased memory functions.
Anxiety
Studies show that cannabis can be both anxiogenic and anxiolytic. It has been determined that low doses of Δ9-THC have an anxiolytic effect, whereas high doses of Δ9-THC have an anxiogenic effect. In the same study, it was found that CBD had an anxiolytic effect by affecting the limbic and paralimbic regions in both animals and humans. In a randomized clinical study using a single dose of 600 mg cannabidiol, 24 participants with generalized social anxiety disorder were included and it was shown that cannabidiol relieved their anxiety related to public speaking compared to placebo. These data explain why many people around the world are turning to cannabis to get rid of anxiety complaints.
anorexia
It is a known fact that people who use cannabis have an increased appetite. Likewise, it is stated that THC and other CB1 agonists have appetite-increasing effects. In experiments conducted by Scherma and his colleagues in an anorexic rat model in 2017, they found that both natural A9-THC and its synthetic form reduced the weight loss and increased the activity of rats by increasing leptin signaling and reducing plasma corticosterone levels. Many studies suggest that CB1 stimulation can increase appetite and reduce weight loss in anorexic patients or severe anorexia due to cancer. Dronabinol, a synthetic THC derivative, has been used in the treatment of anorexia in AIDS patients since 1992.
Diabetes
In the diabetic rat model, it has been understood that cannabidiol slows down β cell damage by reducing the release of IL-12 from macrophages and plasma IFN-γ levels, and therefore studies on the importance of endocannabinoids in diabetes are increasing. However, the evidence regarding this main mechanism is not yet sufficient. However, it has been determined that in diabetes, glutathione reserves in the liver are significantly reduced and lipid peroxidation increases. In a study conducted in diabetic rats, CBD was found to increase glutathione reserves in the liver and, accordingly, reduce lipid peroxidation. This study also found that low NGF concentrations, one of the mechanisms responsible for diabetic neuropathy, can be increased by CBD treatment. Another study demonstrated that CBD and THC have higher antioxidant activities than α-tocopherol and ascorbate [87]. When all these data are evaluated, it is possible to say that cannabis is promising, especially in complications involving oxidative mechanisms such as diabetic neuropathy, but further research on other mechanisms is needed.
Epilepsy
Many preclinical studies have shown that cannabinoids can be used in epilepsy. Although preclinical and clinical studies conducted with CBD and cannabidivarin, the propyl derivative of CBD, reveal an anticonvulsant effect, the mechanism of this effect has not been fully elucidated [88]. In the study conducted by Szaflars et al. in 2018 with 72 children and 60 adults, it was observed that CBD treatment significantly relieved epileptic symptoms. Following these studies, the FDA approved the CBD-containing drug called “Epidiolex” for use in the treatment of Lennox-Gastaut syndrome and Dravet syndrome, two severe and rare forms of epilepsy. Finally, Aran et al., in their retrospective study, stated that CBD is a safe, tolerable and effective treatment for persistent behavioral problems in children with ASD (atrial septal defect). Considering all these data, it seems that phytocannabinoids, especially CBD, have a high treatment potential in various seizures, epilepsy and other neurodegenerative disorders.
Nausea and Vomiting Accompanying Chemotherapy
As it is known, nausea and vomiting are among the most common side effects of drugs used in cancer chemotherapy. It is known that THC and cannabidiol prevent nausea and vomiting through CB1 receptors and some other mechanisms. Dronabinol and nabilone have been used clinically since the 1980s to relieve chemotherapy-induced nausea and vomiting, especially in cancer patients who cannot get results with conventional antiemetics.
Chronic Pain
As it is known, one of the first discovered effects of cannabis on human health is its analgesic activity. Medical cannabis users also use cannabis mostly due to this effect [90]. Migraine, bone and joint pain, menstrual cramps, etc. Although it is effective in many types of pain, its effectiveness is much higher, especially in difficult-to-treat pain types that do not respond to conventional treatments, such as neuropathic pain and cancer pain. For this purpose, the standardized hemp extract nabiximols containing THC and CBD has been used in the clinic since 2010.
Colitis
Different preparations of hemp are used for gastrointestinal pains, gastroenteritis, diarrhea, etc. It has been known to be used for a long time in many gastrointestinal diseases [91]. Phytocannabinoids such as CBC, CBD and CBG have been reported by various researchers to play an anti-inflammatory role in inflammatory bowel disorders in various experimental models. In the study conducted by Nallathambi et al., it was determined that Δ°-THCA had anti-inflammatory properties in colon epithelial cells.
Spasticity Due to Multiple Sclerosis
Currently, drugs used to treat multiple sclerosis symptoms such as muscle spasticity, neuropathic pain, tremor, ataxia and neurogenic bladder are not fully therapeutic and their use may be limited due to their side effects [96]. This is the reason why cannabis is increasingly being tried by multiple sclerosis patients all over the world. After 2010, nabiximols began to be used in many countries, especially Canada and most European countries, in the treatment of spasticity and pain due to multiple sclerosis that did not respond to conventional treatments. Psychoactive side effects and resistance were reported at very low levels during these treatments, and patients tolerated the treatment well.
Schizophrenia and Other Psychoses
Cannabidiol has been shown to inhibit the psychoactive effects of THC and also has positive effects on metabolic, inflammatory and stress-related symptoms in schizophrenia [98]. In a randomized double-blind clinical study conducted by Leweke et al., cannabidiol and amisulpride treatment were compared in 42 schizophrenia patients at the end of 4 weeks, and cannabidiol treatment was found to be superior because it reduced psychotic symptoms more effectively and had fewer side effects.
Sleeping disorders
There are studies showing that short-term treatments with nabilone and dronabinol may be beneficial in obstructive sleep apnea. Studies have proven that nabilone also reduces nightmares due to post-traumatic stress disorder and improves sleep quality in patients with chronic pain.
Tourette Syndrome
Tourette Syndrome (TS) is a neurodevelopmental disorder characterized by motor and vocal tics lasting at least one year, with a frequency of 0.4-0.6% in childhood. Some clinical studies have proven that chronic cannabis or dronabinol therapy reduces tics in treatment-resistant Tourette syndrome.
RESULTS AND DISCUSSION
As can be seen, hemp is a medicinal plant that has been used by humanity for human and animal health for thousands of years and has gained an important place in traditional medical systems such as Chinese medicine and Ayurveda, which have their own philosophy and thousands of years of experience. In the following years, the abuse of cannabis due to its psychoactive effects led to its ban despite its superior uses in numerous areas. However, approximately 550 more compounds have been identified in hemp, other than Δ9-THC, the main compound that caused its ban. Moreover, scientific studies have revealed that A9-THC has a therapeutic effect on many diseases, especially neurodegenerative diseases such as Alzheimer’s, nausea, vomiting and anorexia. Apart from the effects of cannabis on the diseases or symptoms mentioned in the article; glaucoma, post-traumatic stress disorder, depression, Huntington’s disease, Parkinson’s disease, dystonia, etc. Studies are also being conducted on its use in other diseases.
In order to fully reveal the potential effects of cannabis, which has such a high and diverse therapeutic potential, to elucidate the treatment mechanisms, and to predict possible side effects during chronic treatments, it would be appropriate to investigate the action mechanisms of effective compounds in detail and conduct further clinical studies.