The importance of the switch process as the hallmark of BPD was described in Falret’s original (1854) conceptualization of ‘circular insanity’, which he defined as a form of illness in which “depression and
mania must succeed one another for a long time, usually for the whole of the patient’s life, and
in a fashion very nearly regular, and
with intervals of rationality, which are usually short compared with the length
of the episodes”1 (translated into English by Sedler and
Desain2, page 1130).