Only a few studies have looked into the use of cannabinoids for hearing loss, tinnitus, or balance disorders, suggesting the need for further research. Some of the latest articles in the U.S. National Library of Medicine include the study by Tabrizi, et al., who reported the potential of endocannabinoids to inhibit the action of a receptor (TRPV1) that responds to noxious stimuli, causing pain and injury to the cell.15 The TRPV1 receptor activation is considered responsible for the pathology development of cystitis, asthma, epilepsy, diabetes, and hearing loss. The use of antagonists, including CBD, to target this receptor may have a clinically therapeutic potential.
Fiskerstrand and colleagues identified a gene mutation that produces an error in endocannabinoid metabolism, which resulted in a multifocal debilitating neurodegenerative disease.16 PHARC affects the peripheral and central nervous systems, causing impaired vision and hearing loss. The gene mutation disrupts the metabolism of endocannabinoids, reducing the cells that remove damaged cells and infection, while dysregulating neurogenesis.
In tinnitus research, Smith and Zheng17 investigated if cannabinoid receptor activation could create a pro- or antiepileptic action in the cochlear nucleus and if cannabis could make tinnitus better or worse. The results of this research were inconclusive.
The use of antineoplastic drugs, particularly cisplatin, has been shown to result in hearing loss. Ghosh, et al.,18 evaluated the use of endocannabinoids delivered via transtympanic administration to rats that were subsequently injected with cisplatin. The results “support the role of the endocannabinoid/CB2R system in maintaining normal hearing in the rat cochlea.” The authors concluded that the use of transtympanic injections of agonists to the CB2 receptor provided effective protection against cisplatin-induced hearing loss.
Acoustic trauma is an area that is widely researched. The formation of free radicals and reduced blood flow are key players in the cochlea. It has also been shown that tinnitus has a central representation and that antiepileptic drugs are sometime used as a treatment. Zheng, Reid, and Smith19 investigated whether THC and CBD delivered to rats could provide relief from tinnitus. Their findings suggest that cannabinoids may increase the occurrence of tinnitus in noise-exposed rats, especially when there is prior hearing damage.
In hearing care, further investigation into the benefits of cannabis is needed, particularly in the treatment of debilitating tinnitus and hyperacusis with comorbid sleep deprivation and psychopathology.20