**3.6 Jet lag disorder (JLD)**

ICSD-3 Diagnostic Criteria [6]:


Clinical Characteristics: JLD occurs when an individual travels through time zones faster that the endogenous circadian rhythm can adjust, resulting in desynchrony between the external light–dark cycle and one's internal clock. Symptoms of JLD include difficulty falling and staying asleep, excessive daytime sleepiness, generalized fatigue, impaired daytime performance, and various somatic symptoms (most commonly gastrointestinal) that begin 1 to 2 days post-travel [8].

In addition to number of time zones traveled, the severity of jet lag is affected by the direction of travel. Eastward travel leads to more difficulty with falling asleep and is more difficult to adjust to, while westward travel is more disruptive to sleep maintenance.
