Prolonged separation from family and friends back home is a huge source of stress for people in isolated, confined environments, Palinkas said.

CNN: 501 days in space with your spouse: Could you handle it?

Based on Palinkas' studies at the South Pole, the most stable individuals and those with the most stable relationships are middle-aged married couples.

CNN: 501 days in space with your spouse: Could you handle it?

But there is some evidence from extreme environments on Earth to support the married couple idea, says Lawrence Palinkas of the University of Southern California, who has studied more than 1, 000 Americans who have spent winters in Antarctica over a four-decade period.

CNN: 501 days in space with your spouse: Could you handle it?