Although travel can be fun, according to the Madrid College of Psychologists, it can also expose the traveller to obvious and hidden dangers, which can lead to illness or aggravate existing health problems. Lack of sleep, combined with stress, dehydration, increased levels of exertion, musculoskeletal strains and changing health care delivery systems can all affect the traveller, but some disorders are caused by the process of moving from one part of the world to another. Thus, the four most common conditions caused by travel are:
- Altitude sickness: Travelling to high altitudes exposes people to increasingly rarefied air and a decreasing amount of oxygen, resulting in a decrease in blood oxygen levels, which can lead to impaired physical and mental performance. The response to altitude varies, but most people can function normally at altitudes up to 2,438 metres above sea level. At higher altitudes, oxygen deficiency can begin to cause a condition known as acute mountain sickness (AMS). At altitudes above 3,048 metres, 75% of people experience at least mild symptoms of AMS.
- Paris Syndrome: associated with delusions, hallucinations, persecution complexes, loss of connection with reality, anxiety, sweating and increased heart rate and sexual desire. Fortunately (or unfortunately, if you are from a particular Pacific archipelago), Paris syndrome usually only affects Japanese tourists visiting Paris. It affects about 20 victims a year, usually women in their 30s. Although the chances of an individual being affected are slim, the threat is considered great enough for the Japanese embassy in Paris to maintain a round-the-clock hotline for travellers at risk.
- Jet Lag: Long-distance travel where several time zones are crossed in a short period of time can cause what is known as jet lag, also known as rapid time zone shift syndrome or desynchronisation. This disorder is caused by the circadian rhythm - the internal clock, which is tuned to the day-night cycle at the place of departure - being out of sync with the day-night cycle at the destination, with little or no time to adjust. Jet lag affects air travellers in particular because of the greater distances and time zones covered in a relatively short time. Navigators may have some difficulty with this condition if they do not regularly settle in while travelling the world.
- Post Traumatic Stress Disorder (PTSD): a range of behaviours and emotional reactions often develop in response to life-threatening situations. These symptoms may consist of flashbacks or reliving the incident, either in dreams, uncontrollable memories or hallucinations, or hypervigilant reactions to normal stimuli, such as performing evasive manoeuvres when hearing a dropped plate.
- Motion sickness: Motion sickness - commonly known as motion sickness - is any disorder caused by motion, such as seasickness, airsickness or car sickness, as defined in Taber's Cyclopean Medical Dictionary. It is a common ailment of travellers on ships or aeroplanes, in motor vehicles and even when riding animals such as horses. Most people, including experienced sailors and frequent air travellers, have experienced seasickness at one time or another. All that is needed is a sufficiently strong stimulus, which can vary greatly from person to person. Most people acclimatise - or "get their sea legs back" - over time, but the process can take up to two or three days.