Severity of insomnia is judged along dimensions of frequency, intensity, and duration, as well as impact on daytime functioning and quality of life. Generally, the criteria for severe and chronic insomnia are a minimum duration of 6 months with problems presenting at least four nights per week. Restlessness, irritability, anxiety, daytime fatigue, and tiredness commonly accompany such presentations. Mild and moderate insomnia may be diagnosed where problems are less intrusive.
Most patients presenting with insomnia have psychophysiological difficulty initiating and/or maintaining sleep. Usually marked functional effects and somatized tension associated with sleep are evident. The patient reports extreme tiredness while being unable to sleep satisfactorally. This contrasts with the circadian disorders where, in delayed sleep-phase syndrome, the patient may not feel sleepy until late in the normal sleep period, and in advanced sleep-phase syndrome, may waken early and be unable to return to sleep. Taking a history, incorporating screening questions on restlessness, limb movements, and breathing can help to diagnose obstructive sleep apnoea syndrome, periodic limb movement disorder, and restless legs syndrome, although full polysomnographic evaluation is usually also required.(5) However, polysomnography is not essential for the diagnosis of insomnia, for which sleep diary monitoring (see ChapieL.4.1,4...!) is usually the most useful form of assessment.(2) Wrist actigraphy is an inexpensive objective evaluation, which estimates sleep/wakefulness based upon body movement.(6) Continuous recordings can be made over five to ten consecutive 24-h periods. It is useful in identifying sleep state misperception and charted data can be inspected for circadian anomalies, as in delayed sleep-phase syndrome and advanced sleep-phase syndrome.
Extrinsic causes of insomnia are reported in Table 1 and should not be overlooked. In particular, hypnotic dependent sleep disorder is associated with benzodiazepine drugs where withdrawal leads to exacerbation of the primary problem.(7) This can be mistaken for a severe underlying insomnia and hence reinforce hypnotic dependency.
A wide range of psychiatric conditions, particularly affective disorders, have associated sleep symptomatology (see Chapter..4.!4.5). For example, a primary diagnosis of psychophysiological insomnia cannot be made where diagnostic criteria for DSM-IV Axis I or Axis II disorders are fulfilled. Similar caveats apply to insomnia associated with medical disorders (see Chapter4.14.6).
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