The stress of international travel can lead to mental disorder in vulnerable people, the World Health Organisation has warned.

Reports said the body has for the first time included detailed guidance on the psychological impact of travel in its annual publication, International Travel and Health.

Mental problems, it said, were among the leading causes of ill-health among travellers.

It also mentioned psychiatry emergency alongside injury and heart disease as the commonest medical reasons for evacuation by air ambulance.

Meanwhile an air charter firm based in New York said it had flown a passenger with bipolar disorder from Egypt back to Manchester after he became manic.

A key problem faced by travellers, according to the WHO, is extreme anxiety such as phobia of flying, which constitutes up to 3.5 per cent of all medical in-flight emergencies.

Travellers are continuously warned by experts to make sure they take out comprehensive travel insurance to cover them in case of medical emergencies and other unforeseen events during their trip.