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Although insomnia
accompanies many diseases, it is also seen in primary form, i.e.
not associated with any obvious mental or physical illness. This
means that insomnia can be a symptom (when associated with another
disease) or a sleep problem and diagnosis in its own right. Several
classification systems exist for sleep problems (including insomnia)
and these systems are not always consistent with one another.
Click
here for a table comparing four common classification schemes.
Primary insomnia
may be acute (transient) or chronic (persistent). According to
the International Classification of Sleep Disorders (ICSD) acute
is defined as < 1 month duration, subacute (1-6 months)
and chronic (>6 months). Transient insomnia often accompanies
stressful situations (e.g. death of a spouse, major catastrophes).
The propensity to experience chronic primary insomnia is thought
to be related to a personality style skewed towards hyper-arousal
(emotional stress) and hyper-activation (physiological stress),
which in turn are shaped by both genes and environment. Family
history has been shown to be a risk factor (Bastien
and Morin, 2000). Numerous behavioral factors can contribute
to disrupted sleep (Hajak,
2000):
- Substance
abuse;
- Medications
(e.g. corticosteroids, thyroid hormones, and many others);
- Dysynchrony
with circadian light/dark cycles;
- Sleep-disruptive
lifestyles.
Chronic insomnia
can have profound personal, social, and economic consequences
such as the following (Leger,
2000):
- Excessive
daytime sleepiness;
- Poor attention,
memory, and problem-solving abilities;
- Impaired
reaction times;
- Social
instability;
- Fewer
job promotions;
- Increased
job absenteeism;
- Higher
rate of traffic or occupational accidents;
- More frequent
medical problems;
- Higher
hospitalization rates.
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