When a person couldn't sleep, has interrupted sleep, or is still tired after sleeping; and the condition recurs for more than two nights every week for more than one month. Also, it is characterized when the patient is fatigued and believes that his daily activities are affected by this sleeping condition.

Based on the causes, chronic insomnia may be further characterized into primary or secondary:

* Primary chronic insomnia - when the insomnia is not caused by any physical or mental imbalance.
* Secondary chronic insomnia - may be caused by physical and mental conditions, such as depression, or emotional and psychiatric disorders.

In one study, in industrialized nations, chronic insomnia affects about ten percent of adults.