Diagnostic Considerations
Jet lag should be differentiated from delayed sleep-phase syndrome (DSPS). DSPS should be differentiated from lifestyle preference, inadequate sleep hygiene, primary insomnia, and psychiatric conditions. (Psychopathology has been found in 50% of patients with DSPS.)
Transient circadian rhythm disturbances define themselves by their timing. Many psychiatric conditions distinguish themselves by short sleep times and disrupted sleep. Regardless of their bedtime, patients with psychiatric disorders have sleep-onset insomnia. Coping styles distinguish the night owl.
Advanced sleep-phase disorders should be differentiated from atypical depression, seasonal affective disorder, and excessive daytime sleepiness (EDS) associated with other sleep disorders.
Patients with irregular sleep-wake schedules are distinguished by the irregularity not only of their sleep cycle, but also of their cycles of eating and other daily activities. The rhythm of body temperature also is affected. Irregular sleep-wake schedules should be differentiated from psychiatric disorders and from insomnia associated with shift work.
Daytime sleepiness in DSPS should be distinguished from sleep-disordered breathing, narcolepsy, and atypical depression. All of these conditions often present with early bedtime.
Nocturnal eating disorder may also have a substantial impact on circadian cycles, with frequent awakenings for feeding. Sleep distribution may resemble that of infants, with sleep and feeding distributed over a 24-hour period.
Insomnia is a core feature of posttraumatic stress disorder and has been reported in 70% of patients.
