320 Insomnia
deprivation (Rechtschaffen et al., 1983). In humans, there is
little evidence that total sleep loss, even for several days, pro-
duces any permanent or severe physical or psychological dys-
function (Horne, 1986). The most prominent effect of sleep
deprivation is an increased feeling of sleepiness and desire
for sleep. After one or two nights without sleep, most individ-
uals will show microsleep episodes intruding into wakeful-
ness, which will produce lapses of attention. These cognitive
impairments are found mainly on tasks requiring sustained at-
tention and rapid reaction time. Processes involved in safe
and vigilant driving are particularly sensitive to sleep depri-
vation. Executive functions such as judgment, creativity, and
mental ”exibility are also altered after prolonged sleep loss
(Horne, 1988; Johnson, 1982; Parkes, 1985). Changes in
mood have been noted after as little as one night of total sleep
deprivation. Individuals tend to be more irritable, and show
less motivation, interest, and initiative. Conversely, acute
sleep deprivation may have a transient antidepressant effect
in persons with major depression (Gillin, 1983); this effect is
very short-lived as mood returns to baseline after the “rst
sleep episode. The few reports of personality changes or
psychotic-like behaviors after prolonged sleep loss have been
related to special contexts such as in combat situations
(Horne, 1988; Parkes, 1985).
Although total sleep deprivation for more than one night is
relatively rare, partial sleep loss is far more common. Indi-
viduals with sleep disorders usually experience partial sleep
deprivation. For example, insomnia sufferers can experience
partial sleep loss for years before consulting a professional.
Patients with sleep apnea (a sleep-related breathing disorder)
or with medical conditions producing chronic pain often
show sleep fragmentation and frequent awakenings, which
are followed by severe daytime sleepiness. The consequences
of prolonged sleep deprivation, even partial, can be very seri-
ous with regard to performance, quality of life, and public
health safety. For example, in situations where sustained
attention is needed, while driving or while operating heavy
industrial machinery, sleep-deprived individuals may put
themselves and others at great risk. Several major accidents
have been linked to fatigue and sleep deprivation (Mitler
et al., 1988).
INSOMNIA: SCOPE OF THE PROBLEM
Insomnia entails a spectrum of complaints which re”ect dis-
satisfaction with the quality, duration, or ef“ciency of sleep.
These complaints can involve problems falling asleep, main-
taining sleep throughout the night, or early morning waken-
ing, either alone, or in combination. Individuals complaining
of insomnia may also describe their sleep as light and non-
restorative. Insomnia is almost always accompanied by re-
ports of daytime fatigue, mood disturbances (e.g., irritability,
dysphoria), and impairments in social and occupational func-
tioning. Other prominent clinical features are the extensive
night-to-night variability in sleep patterns and the discrep-
ancy that is often present between the subjective complaint of
insomnia and objective measures of sleep (Morin, 1993).
As virtually everyone experiences an occasional poor
night•s sleep at one time or another, it is important to consider
the frequency, intensity, and duration of sleep dif“culties to
determine their clinical signi“cance. Several criteria are used
to operationalize insomnia complaints in outcome research.
These include a sleep-onset latency and/or wake-after-sleep
onset greater than 30 minutes, a sleep ef“ciency (ratio of total
sleep time to time spent in bed) lower than 85%; and sleep
dif“culties that are present three or more nights per week
(Morin, 1993). Insomnia is situational if it lasts less than one
month, subacute if it lasts between one and six months, and
chronic when it persists for more than six months. Because of
individual differences in sleep needs, total sleep time is not a
good marker of insomnia when considered alone.
According to the International Classification of Sleep
Disorders(ICSD; American Sleep Disorders Association
[ASDA], 1997), there are several broad classes of sleep-wake
disorders including the insomnias, hypersomnias, parasom-
nias, and sleep-wake schedule disorders. Within the insomnia
category, an essential distinction is made in both the Diag-
nostic and Statistical Manual of Mental Disorders(4th ed.,
DSM-IV;American Psychiatric Association [APA], 1994)
and the ICSDbetween primary and secondary insomnias: the
former represents an independent disorder unrelated to any
other co-existing condition, while the latter encompasses
sleep disturbances etiologically linked to another mental or
physical problem. Table 14.1 depicts a modi“ed and updatedTABLE 14.1 Primary and Secondary Insomnia Subtypes according
to the ICSD
Primary insomnias.
Psychophysiological insomnia.
Subjective insomnia (sleep state misperception).
Idiopathic insomnia (childhood onset).
Secondary insomnias.
Insomnia associated with psychiatric disorders.
Insomnia associated with medical or central nervous system disorders.
Insomnia associated with alcohol or drug dependency.
Insomnia associated with environmental factors.
Insomnia associated with sleep-induced respiratory impairment.
Insomnia associated with movement disorders.
Insomnia associated with sleep-wake schedule disorders.
Insomnia associated with parasomnias.