Primary insomnia is sleeplessness that is not attributable
to a medical, psychiatric, or environmental cause. The
diagnostic criteria for primary insomnia from the Diagnostic
and Statistical Manual of Mental Disorders, Fourth Edition
(DSM-IV) is as follows:
Predominant complaint is difficulty
initiating or maintaining sleep or non-restorative sleep
for at least 1 month.
Sleep disturbance (or associated daytime
fatigue) causes clinically significant distress or impairment
in social, occupational, or other important areas of
Sleep disturbance does not occur exclusively
during the course of narcolepsy, breathing-related sleep
disorder, circadian rhythm sleep disorder, or parasomnia.
Disturbance does not occur exclusively
during the course of another mental disorder (eg, major
depressive disorder, generalized anxiety disorder, delirium).
Disturbance is not due to the direct
physiologic effects of a substance (eg, drug abuse,
medication) or a general medical condition.
The primary components involved are intermittent periods
of stress, which result in poor sleep and generate 2 maladaptive
behaviours, (1) a vicious cycle of trying harder to sleep
and becoming tenser, expressed as "trying too hard
to sleep," and (2) bedroom and other sleep-related
activities (eg, brushing teeth) conditioning the patient
to frustration and arousal.
Bad sleep habits such as those naturally acquired during
periods of stress occasionally are reinforced and, therefore,
are prevented from extinction and become persistent. Thus,
the insomnia continues for years after the stress has
abated and is labelled persistent psycho-physiological
Lifelong sleeplessness is attributed to an abnormality
in the neurological control of the sleep-wake cycle involving
many areas of the reticular activating system (promoting
wakefulness) as well as areas such as solitary nuclei,
raphe nuclei, and medial forebrain area (promoting sleep).
Possibly, a so-called neuroanatomic, neurophysiologic,
or neurochemical lesion exists in the sleep system in
which patients tend to be on the extreme end of the spectrum
Sleep state misperception
Complaint of insomnia occurs without objective evidence
of any sleep disturbance.
Frequency: Primary insomnia is diagnosed in approximately
15% of patients with insomnia who are referred to sleep
disorder centres following exclusion of other predisposing
conditions. However, true incidence is not known.
Mortality/Morbidity: Whether the consequences
associated with chronic insomnia outweigh the costs of
treatment remains debatable. Despite that, the following
associations have been noted: