An active cortex is necessary for intact cognitive function. In a sleepy individual, the cerebral cortex is to some extent deactivated; a sleep-deprived person will experience reduced physical and mental activity and productivity, more errors on the job, more risk for motor vehicle accidents, and psychosocial problems. Hormone levels can become imbalanced from excessive daytime sleepiness (EDS), and treatments for conditions unrelated to EDS can be hampered. Whether sleep restriction is voluntary or not, those who experience it habitually are at greater risk of obesity and type 2 diabetes. While an accurate history is necessary to diagnose sleep disorders, all too often a patient's chronic daytime sleepiness is never mentioned. EDS will not show up in most blood chemistries either. It is important that primary care providers ask patients about their sleep and its quality. Other screening tools include questionnaires, which are easily administered and can be sensitive. To determine the basis of EDS, formal sleep studies may be necessary.