This might explain it ...
Why holidays can be bad for your health
World Health Organisation issues warning on stress and offers tips for travellers
By Jeremy Laurance, Health editor
Travel is said to broaden the mind – but it can also damage it, experts say.In an unprecedented move, the World Health Organisation (WHO) has issued a warning that the stress of international travel can lead to mental disorder in vulnerable people.
Why holidays can be bad for your health - Health News, Health & Wellbeing - The Independent
The bit that got my attention was ...
"Psychiatric emergency" is one of the most common medical reasons for evacuation by air ambulance, along with injury and heart disease, the WHO report says. Up to 100 patients a week are brought back to the UK by air ambulance, according to the British Ambulance Association, and many more are returned on commercial aircraft, mostly accompanied by medical staff.