Here's a troubling insight on the relationship of physical and mental torture from Ian Buruma's recent review (
http://www.nybooks.com/articles/archives/2014/jan/09/china-r...) of a book on Maoist China:
In most accounts, the distress caused by endless indoctrination, public denunciation, and self-criticism was worse than physical torture. Physical pain still allows the victim to retreat into himself. After days, months, years of mental torture there is no longer a self to retreat into. Besides self-abasement, victims were made to show their sincerity by persecuting others, sometimes friends or relatives. In many cases, suicide was the only way out. But ideally, if a person had finally reached the stage when his confessions were totally convincing, there was no longer any gap between acting and natural behavior, between faked and true thoughts. The process ended, in the phrase of a Chinese former victim, with “the physical and mental liquidation of oneself by oneself.”