Insomnia Insomnia

Differential Diagnosis of Insomnia 43
Psychiatric Conditions
When anxiety permeates most aspects of functioning in patients with insomnia,
generalized anxiety disorder is the usual diagnosis. In contrast, if anxiety is focused
almost exclusively on poor sleep and its consequences on daytime functioning, psychophysiological
insomnia is the typical diagnosis (28)
Insomnia due to affective disorders is sometimes difficult to differentiate from
psychophysiological insomnia because a dysphoric mood, ascribed to the effects of
poor sleep, often accompanies psychophysiological insomnia. The two conditions
can often be distinguished on the basis of other “vegetative” signs, such as loss of
appetite or libido or the typical diurnal fluctuation (worse in the morning) of depression
(28). In general, a diagnosis of psychophysiological insomnia is inappropriate if
the patient fulfills criteria for any other Axis I or II diagnosis in the fourth edition of
the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (29).
Medication-Induced Insomnia
Selective serotonin reuptake inhibitors (30), stimulants, theophylline, prednisone,
and two of the newer anticonvulsants, felbamate (31) (Felbatol) and
lamotrigine (32) (Lamictal), may cause insomnia. Other medication or chemically
related causes of insomnia include withdrawal from sedative agents, idiosyncratic
reactions to other medications, and toxin-related reactions (e.g., alcohol, carbon
monoxide [33], inorganic mercury [34], recreational drugs). A thorough list of the
patient’s medications and chemical exposures is essential for the evaluation of
insomnia.
DIAGNOSTIC TOOLS
PSG and Multiple Sleep Latency Test
The PSG is a polygraph of EEG findings, eye movements, electromyography
readings, oxygen saturation, limb movements, airflow, and chest and abdominal
movements taken during sleep, usually for the entire night. According to the American
Sleep Disorders Association (now the American Academy of Sleep Medicine),
practice parameters polysomnography is not indicated in routine evaluation of
insomnia, except when the diagnosis is uncertain and a primary sleep disorder is
suspected and when insomnia does not respond to appropriate behavioral and pharmacological
treatments (35).
A Multiple Sleep Latency Test (MSLT) is a series of four or five opportunities,
each separated by a 2-hour interval, to take a 15- to 20-minute nap. It is used to
assess sleep latency and the possibility of such sleep disorders as OSA and narcolepsy.
In primary insomnia, results of the MSLT are usually normal (36).
Sleep Logs
A sleep log (Fig. 1) is a graph on which, for 2 to 3 weeks, the patient records
bedtime, approximate sleep time, times and duration of awakenings during the sleep