German doctors are working on ways to help astronauts avoid the dangers of depression and boredom, which they say will be a key issue for long space missions like the one planned to Mars. Depression can demotivate astronauts and affect their ability to concentrate. Although astronauts are carefully screened for psychological well-being, the extreme pressures of space travel means depression can take hold, according to Dr. Klaus Legner, from the European Space Agency (ESA) Medical Support Office. The psychological pressure on crews, including long periods of isolation, could manifest themselves as anything from loneliness to arguments caused by enforced habitation of a small space with others, he said.