Neurodegenerative diseases (NDDs) are growing in frequency and represent a major threat to public health. Advances in scientific progress have made it clear that NDDs share many underlying processes, including shared intracellular mechanisms such as protein misfolding and aggregation, cell-to-cell prion-like spread, growth factor signaling abnormalities, RNA and DNA disturbances, glial cell changes, and neuronal loss. Transmitter deficits are shared across many types of disorders. Means of studying NDDs with human iPS cells and transgenic models are similar. The progression of NDDs through asymptomatic, prodromal, and manifest stages is shared across disorders. Clinical features of NDDs, including cognitive impairment, disease progression, age-related effects, terminal stages, neuropsychiatric manifestations, and functional disorders and disability, have many common elements. Clinical trials, biomarkers, brain imaging, and regulatory aspects of NDD can share information across NDDs. Disease-modifying and transmitter-based therapeutic interventions, clinical trials, and regulatory approaches to treatments for NDDs are also similar.