In addition to physical difficulties, astronauts who travel for long periods may also suffer from psychological stress. Space travel requires astronauts to be very focused, balanced people.
The irregular sleep long working hours and the lack of night and day can affect a person’s emotions and stress level. Being able to control one’s emotions is an important characteristic for an astronaut.
A major factor that affects astronauts' mental well-being is time.
To date astronaut
have only spent a few months in space at a time but longer expeditions would
require astronauts to spend significantly more time inside a spaceship.
For example a round-trip expedition to Mars could take about three years. Being confined in a small space for such a long period of time is not healthy.