type–related episodes of mania resulting from missed nights of sleep. Shift work type of-
ten results in interpersonal problems. 
Differential Diagnosis
Normative variations in sleep with shift work. The diagnosis of shift work type, as op-
posed to the “normal” difficulties of shift wo rk, must depend to some  extent on the sever-
ity of symptoms and/or level of distress experienced by the individual. Presence of shift
work type symptoms even when the individual is able to live on a da y-oriented routine for
several weeks at a time may suggest the presence  of other sleep disord ers, such as sleep ap-
nea, insomnia, and narcolepsy, which should be ruled out. 
Comorbidity
Shift work type has been associated with in creased alcohol use disorder, other substance
use disorders, and depression. A variety of physical health disorders (e.g., gastrointestinal
disorders, cardiovascular disease, diabetes, ca ncer) have been found to be associated with
prolonged exposure to shift work.
Relationship to Internat ional Classification of 
Sleep Disorders
The International Classification of Sleep Disorders,  2nd Edition (ICSD-2), differentiates nine
circadian rhythm sleep disord ers, including jet lag type.