Regenerative dissonance

Regenerative dissonance was a mental illness seen in Time Lords. It occurred when the personalities of a Time Lord's previous incarnations lived on inside the body of their current incarnation, exerting just as much influence on the body as the personality of the current incarnation.

The Time Lord calling himself the Eleven by his eleventh incarnation suffered from this. His previous selves went by a number sequence in order of incarnations. (AUDIO: The Eleven)

Other Time Lords were known to suffer from this illness, but they often committed suicide as they couldn't cope with the voices. The Time Lord who lasted the longest with this condition after the Eleven died after shooting out both his hearts with a staser in his eighth body. (AUDIO: World of Damnation)