The effects of attunement with the Body Cosmic can be reversed. An extended stay planetside, extended mental stasis without biostasis - anything that allows the tissues in the body to regenerate and cycle out without accumulating more cosmic energy. However, the power of the Body Cosmic can, and most likely will, be responsible for permenant mental damage. The power may be drained from the individual, but not the madness.
These days, no traveler is allowed to offworld for any longer than a month at a time - and even then, their ships and suits must be properly shielded before doing so. All these reduces the amount and duration of exposure to the effects of open space travel. Such measures are necessary, made apparent by a quick excursion into the history of space travel. In the early days, before the issue of the Body Cosmic were apparent, travelers would roam to the far reaches of the solar system, only to return disturbed. These were in the first days of light travel, when fuel issues were more of a problem then then they are now. Whereas these days spacefarers can jaunt several AU in a single burn (the solar system, being approx 100 AU in diameter, can be jumped over the course of 2 months in short bursts from fuel station to fuel station), in those days with few refueling stations and accurate maps and charts, it was quite possible to become lost in the void for a very, very long time. With ample supplies and the right luck, one of these lost souls would return, changed, planetside.
(6,454,861 MPH at max burn, approx - that's across the solar system in 2 months (60 days). 92,956,000 miles in a single AU - speed of light, 670,616,629.2 MPH roughly: .0000001549 % the speed of light at max burn)
The changes were attributed to the then unnamed phenom of the Body Cosmic. Attempts were made to harness the change for... certain purposes that lead to great destruction on several worlds. Since then, experimentation and exposure to the element has been limited a great deal.
Of course, you still have people wandering out to the far rim of space in search of the power the phenomenon promises, thinking themselves fit to deal with the consquences of madness that come with it.
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