Insomnia

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 functioning.
• 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.

Psycho-physiological insomnia
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 insomnia.

Idiopathic insomnia
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 toward arousal.

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:

• Increased risk of mortality is associated with short sleep lengths.
• Insomnia is the best predictor of the future development of depression.
• Increased risk exists of developing anxiety, alcohol and drug use disorders, and nicotine dependence.
• Poor health and decreased activity occur.
• Onset of insomnia in older patients is related to decreased survival.
• Primary insomnia is more common in women than men.

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