How do naps affect your nighttime sleep quality?

Naps can either help or hurt nighttime sleep depending on their timing and duration. Short naps of 10 to 20 minutes taken in the early afternoon generally improve alertness and mood without significantly disrupting nighttime sleep. These brief naps avoid deep sleep stages, so you wake up feeling refreshed rather than groggy. However, longer naps or those taken late in the afternoon or evening reduce sleep pressure, which is the buildup of adenosine that makes you feel sleepy at night. This can make it harder to fall asleep, reduce total nighttime sleep time, and fragment sleep quality. People with insomnia are particularly advised to avoid napping, as it weakens the drive to sleep and reinforces the cycle of poor nighttime rest.