**6.1 Risk factors and genetic pathology of tinnitus**

There are many risk factors known to be associated with tinnitus. To name one of the most common is hearing loss. All the patients with hearing loss may not develop tinnitus, however, individuals with tinnitus have a predictive diagnosis for hearing loss depending on the responses to pure tone thresholds [181]. Other possible risk factors include noise exposure, head trauma, obesity, alcohol consumption, and ototoxic drugs, such as salicylates, quinines and platinum-based drugs can also trigger tinnitus. It can also be found associated with severe otological diseases like Meinnere's disease, acoustic neuroma, and otosclerosis [193].

There are many publications stating the risk factors for tinnitus, but none of them describes the complete mechanism or molecular biology of this disorder. It is speculated that tinnitus is also caused by cochlear or auditory nerve damage. Despite its close relatedness to hearing loss patients suffering from tinnitus do not have the auditory nerve or cochlear degeneration as a common cause. This indicates the involvement of other systems in the brain with or without the involvement of the auditory system.

Determination of heritability of tinnitus remained an important task and it is still an arguable debate in the field. A large study held in Norway shows a significant familial aggregation of tinnitus among the participating population (aged >75 years) [194]. There are few more studies that emphasize the involvement of genetic factors in tinnitus with slight variation in their data [195]. The variation in the results may have appeared due to small sample size or the difference in population characteristics. With the utilization of new scientific technologies, it can be expected that researchers will provide a better and more appropriate conclusion to this debate.
