Psychology MCAT Practice Exam

The correct answer, narcolepsy, is characterized by recurrent and uncontrollable episodes of daytime sleepiness. Individuals with narcolepsy often experience sudden bouts of sleep that can happen at any time, regardless of the amount of sleep they have had the night before. This overwhelming urge to sleep can be triggered by strong emotions or may occur unexpectedly.

Narcolepsy can also involve symptoms such as cataplexy (sudden loss of muscle tone), hypnagogic hallucinations (hallucinations occurring while falling asleep), and sleep paralysis. These features underline the central issue of excessive daytime sleepiness pervasive in narcolepsy.

In contrast, insomnia typically involves difficulty falling or staying asleep and does not inherently cause overwhelming daytime sleepiness but rather fatigue. Sleep apnea is associated with interrupted breathing during sleep, leading to poor sleep quality and excessive sleepiness, but is not classified primarily by episodic sleepiness alone. Somnambulism, or sleepwalking, occurs during non-REM sleep and involves complex behaviors while asleep, rather than episodes of overwhelming sleepiness. Therefore, the defining characteristic of narcolepsy as a disorder of excessive daytime sleepiness makes it the correct answer.