The study examined the effect bilingualism on maintaining cognitive functioning and delaying the onset symptom not only of Alzheimer’s but also the following three most common neurodegenerative diseases to verify, whether bilingualism can be identified as a generalized protective factor. The strengthening of the neural networks, leading to cognitive reserve, increases the resistance of the brain against mental deterioration and eventual brain damage. In this case the linguistic capability stands in direct correlation with the progression of neurodegenerative diseases with the potential of changing its progression. The use of a second language correlates with the activity in key neural networks and allows better coping with damage before the onset of symptoms of the disease, although the varying efficiency along the bilingualism gradient must be considered. The stronger the cognitive reserve, the longer it could compensate for the cognitive decline caused by the initial onset symptoms, allowing a longer life period unaffected by the disease. Bilingualism has already been proven by previous studies to effectively delay onset symptoms of Alzheimer’s, which serves as a basis but this study attempts to expand its sphere of action to all neurodegenerative diseases in general. As aside from Alzheimer’s disease, also Huntington’s, Parkinson’s disease and multiple sclerosis have been studied regarding their connection with cognitive reserve, which strongly correlates with bilingualism. Therefore, to support the universal nature of bilingualism as a protective factor against neurodegeneration the respective underlying mechanisms was analysed as well. The result depicts the expected outcome by initially verifying the effectiveness of bilingualism against the onset of symptoms of Alzheimer’s disease, as well Parkinson’s disease, Huntington’s disease, and multiple sclerosis. The mitigation of the progression rate could only be partially confirmed regarding multiple sclerosis in two of the six studies included. For a universal outcome, further long-term research is required.