Insomnia is a common sleep disorder. People who have trouble falling asleep, staying asleep, or both. As a result, they may get too little sleep or have poor-quality sleep. They may not feel refreshed when they wake up.
Insomnia can cause daytime sleepiness and a lack of energy. It can also make you feel anxious, depressed, or irritable. You may have trouble focusing on tasks, paying attention, learning, and remembering.
Many adults experience insomnia at some point, but some people have long-term (chronic) insomnia. Insomnia may be the primary problem, or it may be secondary due to other causes, such as a disease or medication.