Jet lag is a travel-induced circadian rhythm phenomenon that afflicts healthy individuals following long- distance flights through several time zones. The typical jet-lag manifestations - insomnia during local sleep time, day fatigue, reduced concentration, irritability, and exhaustion with mild depression - are attributed to transient desynchronization in the circadian rhythm until the internal biological clock is rephased to the new environmental conditions. There is strong evidence relating affective disorders with circadian rhythm abnormalities. Less convincing suggestions relate jet lag to psychosis. It can be hypothesized that in predisposed individuals jet lag may play a role in triggering exacerbation or even de novo affective disorders. Furthermore, we propose the possibility that psychosis and even schizophrenia can be elicited by jet lag. This outlook gains its support from case studies and some common underlying phase-advanced biological denominators involved in both jet lag sufferers and psychotic patients.