Insomnia is the feeling of inadequate or poor-quality sleep because of one or more of the following: trouble falling asleep (Initial Insomnia); trouble remaining asleep through the night (Middle Insomnia); waking up too early (Terminal Insomnia); or unrefreshing sleep for at least one month. These can all lead to daytime drowsiness, poor concentration and the inability to feel refreshed and rested upon awakening.
Insomnia is not defined by the hours of sleep a person gets or how long it takes to fall asleep. Individuals vary normally in their need for, and their satisfaction with, sleep. Insomnia may cause problems during the day, such as tiredness, difficulty concentrating and irritability.
Insomnia can be classified as transient, intermittent and chronic. Insomnia lasting from a single night to a few weeks is referred to as transient. If episodes of transient insomnia occur from time to time, the insomnia is said to be intermittent. Insomnia (or Primary Insomnia) is considered to be chronic if it occurs on most nights and lasts a month or more. Secondary insomnia is the symptom or side effect of another problem. This type of insomnia often is a symptom of an emotional, neurological, or other medical or sleep disorder.