What is causing excessive daytime sleepiness?

PREVIEW

Many people have a temporary spell, often in early afternoon, when they feel drowsy. This passing desire for a quick nap is completely different from excessive daytime sleepiness, which is a much more significant problem. Considering the potentially dire personal and economic consequences of falling asleep unintentionally or at inappropriate times, excessive daytime sleepiness must be taken very seriously. A thorough evaluation, as described by Dr Mahowald, virtually always leads to a specific underlying cause, allowing effective treatment recommendations.