Three studies have concluded that obesity and depression are the two main culprits that make people excessively sleepy while awake. Researchers at Penn State examined a random population sample of 1,741 adults and decided that obesity and emotional stress are the main causes of the current "epidemic" of sleepiness and fatigue plaguing America. Insufficient sleep and obstructive sleep apnea also play a role; both have been linked to high blood pressure, heart disease, emotional stress, diabetes, obesity and accidents. "The 'epidemic' of sleepiness parallels an 'epidemic' of obesity and psychosocial stress," Alexandros Vgontzas, MD, the principal investigator for the three studies, said.