US High School Psychology Practice Exam

The disorder that is characterized by overwhelming daytime sleepiness and sudden attacks of sleep is narcolepsy. This condition involves recurring episodes of excessive daytime sleepiness, which can lead to sudden and uncontrollable bouts of sleep that can occur at any time. Individuals with narcolepsy may experience cataplexy, which is a sudden loss of muscle tone triggered by strong emotions, and can also suffer from disrupted nighttime sleep.

In contrast, insomnia involves difficulty falling or staying asleep, resulting in insufficient sleep but does not inherently include daytime sleepiness as a primary feature. Sleep apnea is a disorder where breathing repeatedly stops and starts during sleep, leading to poor sleep quality and daytime fatigue, but it does not specifically manifest as sudden sleep attacks. Hypersomnia refers to excessive sleepiness but is broader and can stem from various causes beyond the distinct and recurring nature of narcolepsy's sleep attacks. Thus, narcolepsy is uniquely defined by its hallmark symptom of unexpected sleep episodes during the day.