Environmental. Hypersomnolence can be increased te mporarily by psychological stress
and alcohol use, but they have not been documented as environmental precipitating
factors. Viral infections have been report ed to have preceded or accompanied hyper-
somnolence in about 10% of cases. Viral infections, such as HIV pneumonia, infectious
mononucleosis, and Guillain-Barré syndrome, can also evolve into hypersomnolence within