According to a NASA study, the medical risks — both physical and psychological — of long journeys in space remain are far greater than the public has been led to believe.
After 40 years of space travel, information on stresses to the body due to space travel has not been properly analyzed. Not enough is known about the dangers of prolonged travel for humans to venture into deep space in a safe and sane manner. Part of the problem comes from ?underreporting? by astronauts about their health problems, due to the confidentiality of data between astronauts and flight surgeons.