Definition
Insomnia may be defined as persistent or repeated difficulties in obtaining adequate sleep. Insomnia may take the form of difficulties initiating sleep, maintaining sleep, waking up too early, or obtaining sleep that is unrestorative or poor in quality. Most patients with insomnia suffer from a combination of these sleep difficulties. Moreover, to be considered insomnia, such sleep difficulties should occur despite adequate sleep opportunity and circumstances for sleep. This helps distinguish insomnia which is a true inability to fall asleep when allowed to, from those individuals who volitionally curtail their sleep for various reasons, or those who have disrupted sleep imposed on them by external factors (eg. firefighters, shift workers etc.). Such sleep difficulties should also be followed by daytime impairment such as fatigue, sleepiness, cognitive difficulties (poor concentration, memory problems etc.) mood changes, decreased motivation, somatic symptoms (headache, gastrointestinal symptoms etc.), impaired performance and social or vocational dysfunction. This helps distinguish insomniacs from short sleepers, individuals who only need a short amount of sleep to feel rested and functional during the day.
A distinction may also be made acute, or a short lived insomnia which may affect all of us from time to time (such as after a period of significant stress or medical illness); and chronic insomnia which represents a more sustained and debilitating condition. Various thresholds have been put forward for what constitutes chronic insomnia, ranging from 30 days to 6 months. The course of insomnia can vary widely between individuals, lasting months to years with periods of remission and periods of exacerbations.
