Insomnia Disorder 367
related psychophysiological symptoms (e.g., tension headache, muscle tension or pain,
gastrointestinal symptoms).
Functional Consequences  of Insomnia Disorder
Interpersonal, social, and occupational problems may develop as a result of insomnia or
excessive concern with sleep, increased daytim e irritability, and poor concentration. De-
creased attention and concentrat ion are common and may be related to higher rates of ac-
cidents observed in insomnia. Persistent in somnia is also associated with long-term
consequences, including increased risks of ma jor depressive disorder, hypertension, and
myocardial infarction; increased absenteeism and reduced productivity at work; reduced
quality of life; and increased economic burden. 
Differential Diagnosis
Normal sleep variations. Normal sleep duration varies considerably across individuals.
Some individuals who require little sleep (“short sleepers”) may be concerned about their
sleep duration. Short sl eepers differ from individuals with insomnia disorder by the lack of
difficulty falling or staying asleep and by the absence of characteristic daytime symptoms
(e.g., fatigue, concentration pr oblems, irritability). However,  some short sleepers may desire
or attempt to sleep for a longer period of time and, by prolonging time in bed, may create an
insomnia-like sleep pattern. Clinical insomnia  also should be distinguished from normal,
age-related sleep changes. Insomnia must also be distinguished from sleep deprivation due
to inadequate opportunity or circumstance for sleep resulting, for example, from an emer-
gency or from professional or  family obligations forcing th e individual to stay awake. 
Situational/acute insomnia. Situational/acute insomnia  is a condition lasting a few days
to a few weeks, often associated with life events  or with changes in sleep schedules. These
acute or short-term insomnia symptoms may also produce si gnificant distress and inter-