Insomnia is the inability to fall asleep or stay asleep, even when you're tired and have the chance to rest. Someone with insomnia might lie in bed for hours, mind racing, unable to drift off. Or they might fall asleep but wake up repeatedly during the night, never getting the deep, restful sleep their body needs.

While everyone has trouble sleeping occasionally, insomnia means this happens regularly, night after night. A student with insomnia might feel exhausted at school, struggling to concentrate during lessons or practice. Athletes with insomnia can't perform their best because their bodies haven't had time to recover and rebuild overnight.

Insomnia can have many causes: worry about an upcoming test, excitement about something happening tomorrow, an uncomfortable sleeping environment, or physical issues that need a doctor's attention.

When someone says they “suffered from insomnia,” they mean they went through a period of repeatedly failing to get adequate sleep. Temporary insomnia might last a few nights during stressful times, while chronic insomnia persists for months or longer. People experiencing ongoing insomnia should talk with a doctor, who can help identify causes and solutions.