So they say anyway:
Although supermax confinement does not produce visible scars or bruises, its impact on prisoners can be comparable to physical torture. As Senator John McCain, who experienced five years of solitary confinement as a prisoner of war, wrote, “t’s an awful thing, solitary. It crushes your spirit and weakens your resistance more effectively than any other form of mistreatment.”
more...
http://www2.nycbar.org/pdf/report/uploads/20072165-TheBrutalityofSupermaxConfinement.pdf
Although supermax confinement does not produce visible scars or bruises, its impact on prisoners can be comparable to physical torture. As Senator John McCain, who experienced five years of solitary confinement as a prisoner of war, wrote, “t’s an awful thing, solitary. It crushes your spirit and weakens your resistance more effectively than any other form of mistreatment.”
more...
http://www2.nycbar.org/pdf/report/uploads/20072165-TheBrutalityofSupermaxConfinement.pdf