What disorder is characterized by excessive daytime sleepiness?

The disorder characterized by excessive daytime sleepiness is narcolepsy. Narcolepsy is a neurological condition that affects the brain's ability to regulate sleep-wake cycles. Individuals with narcolepsy often experience overwhelming drowsiness during the day, which can lead to sudden episodes of sleep or “sleep attacks” at inappropriate times, such as while working or during conversations.

This excessive daytime sleepiness is a hallmark symptom of narcolepsy and can significantly impact daily functioning and quality of life. Unlike other options, narcolepsy is specifically tied to the regulation of sleep stages, making it distinct from ADHD, insomnia, or anxiety disorders, which may impact sleep patterns but do not primarily present with excessive daytime sleepiness as a defining characteristic.