The NASA promise to long-duration space flight includes astronauts who will be returning to the moon as well as those who will take part in human missions to Mars. Successful exploration will require a better understanding of the effects that extended missions pose for the behavioral health of astronauts, not just during flight but also pre and post-flight. The potential for psychiatric disorders developing in long-duration crews during or after missions requires that consideration be given to prevention and treatment .The objective of this study was to validate a ground-based models (Two bed rest conditions such as 6° head-down tilt (HDT) and bed rest position (HB) for microgravity and zero gravity and to study the effects of simulated condition on depression, mood state, back pain and biochemical stress markers. The aim of the present study was to determine the effects of 20-day HDT & HB on psychic stress, depression, mood-state, backache and headache in 10 healthy male volunteers. Psychological state was assessed by a stress test, mood state and cortisol was measured in saliva. During HDT and HB, all volunteers developed psychic stress, and the diurnal rhythm of cortisol secretion was significantly increased in simulated conditions. In addition, urine excretion of dopamine, epinephrine and norepinephrine were significantly increased. Thus 6° HDT & HB appears to be a valid model to induce psychic stress and neuroendocrine-related changes that could also be encountered by astronauts and marsonaunts during long-duration spaceflights.