Insomnia: Scope of the Problem 321version of the insomnia subtypes as outlined in the ICSD
(ASDA, 1997).
The diagnosis of primary insomnia is often made by ex-
clusion (i.e., after ruling out several other conditions); in
addition, it is often based exclusively on the subjective
complaint of an individual, which can be problematic be-
cause there may be signi“cant discrepancies between subjec-
tive reports and objective recordings of sleep. According to
theICSD,there are three subtypes of primary insomnia,
including psychophysiological insomnia, sleep state misper-
ception, and idiopathic insomnia. Psychophysiological in-
somnia is the most classic form of insomnia. It is a type of
conditioned or learned insomnia that is derived from two
sources and whose symptoms can be measured objectively
using polysomnography. The “rst involves the conditioning
of sleep-preventing habits in which repeated pairing of sleep-
lessness and situational (bed/bedroom), temporal (bedtime),
or behavioral (bedtime ritual) stimuli normally associated
with sleep leads to conditioned arousal that impairs sleep.
The second involves somatized tension believed to result
from the internalization of psychological con”icts, dysfunc-
tional beliefs and attitudes about sleep, and performance
anxiety, all of which are incompatible with sleep (Kales &
Kales, 1984; Morin, 1993).
In sleep state misperception, also referred to as subjective
insomnia, the subjective complaint of sleep disturbance is not
corroborated by polysomnographic recording. Although pure
forms of sleep state misperception are rare, most insomniacs
tend to overestimate the time it takes them to fall asleep and
to underestimate their total sleep time. This condition is
present in the absence of malingering or any other psychiatric
disorder. It is unclear whether this phenomenon is due to a
lack of sensitivity of EEG measures, the in”uence of infor-
mation processing variables during the early stages of sleep
(Borkovec, Lane, & Van Oot, 1981; Coates et al., 1983), or
that it simply represents the far end of a continuum of indi-
vidual differences in sleep perception. Interestingly, individ-
uals with subjective insomnia report greater disruption of
daily functioning than those with psychophysiological in-
somnia (Sugarman, Stern, & Walsh, 1985).
Idiopathic insomnia is a condition with an insidious child-
hood onset that develops in the absence of medical or psy-
chological trauma. It is a persistent, lifelong, disturbance
of sleep which can be objectively corroborated with
polysomnography (Hauri & Olmstead, 1980). The underly-
ing cause is suspected to be of a neurological nature as it
often presents in conjunction with other neurologically based
disorders such as attention de“cit hyperactivity disorder.
Despite the presence of daytime sequelae (e.g., memory, con-
centration, and motivational dif“culties), and a more marked
sleep disturbance than that observed in psychophysiological
insomnia, individuals with idiopathic insomnia often experi-
ence less emotional distress than those with the psychophys-
iological subtype, perhaps due to coping mechanisms they
have developed over their lifetime.
The secondary insomnias are considered to be a conse-
quence of or concurrent with another problem. As discussed
in detail later, sleep dif“culties are frequently seen in individ-
uals diagnosed with psychiatric disorders or health problems.
In addition, some individuals experience sleep impairment as
a result of tolerance to or sudden withdrawal from hypnotics.
Either of these situations may lead to a return to or an in-
crease in medication intake and the perpetuation of a vicious
cycle. Environmental factors can also lead to insomnia. Ex-
amples of disruptive environmental sources are light, noise,
temperature, uncomfortable sleeping quarters, disruptive
movements of a bed partner, or the need to remain alert to
danger or the needs of a dependent other (e.g., baby, elderly
parent). In these cases, the cause is considered to be predom-
inantly environmental, although psychological repercussions
are no doubt also present.
Several additional sleep disorders can lead to a subjective
complaint of insomnia (see Table 14.1). Polysomnographic
recordings are usually required to corroborate their presence.
These include sleep apnea, a breathing disorder in which
breathing is impaired during sleep, but remains normal
during wakefulness; restless legs syndrome, a disorder char-
acterized by discomfort and aching in the calves, and the ir-
resistible urge to move the legs; periodic limb movements,
characterized by brief, repetitive, and stereotyped limb
movement during sleep; circadian rhythm disorders, often as-
sociated with jet lag, shift work, and phase-delay and phase-
advance syndromes; and parasomnias, or disorders of arousal
involving an excessively active central nervous system and
provoking episodes of somnambulism and night terrors. The
diverse nature of sleep disturbances makes careful diagnosis
essential, as treatment varies considerably depending on the
characteristics of the disorder.PrevalenceInsomnia is the most common of all sleep disorders. Preva-
lence rates vary considerably across surveys due to differ-
ences in methodology and de“nitions of insomnia. The best
estimates available indicate that about one-third of the adult
population report some problems falling or staying asleep or
are dissatis“ed with their sleep during the course of a year;
about one-third of those, or approximately 10% of the adult
population, complain of persistent and severe insomnia
(Ford & Kamerow, 1989; Mellinger, Balter, & Uhlenhuth,