There is an increasing interest in whether there is a commonality in the observations seen in MRI neuroimaging of a number of conditions, all of which are related to the affective disorders. These four conditions include untreated depression, bipolar disorder, post-traumatic stress disorder, and borderline personality disorder. If such a commonality in MRI findings can be confirmed by a careful meta-analysis, then these common findings may point to a spectrum of affective disorders which is broader than has been suggested until now and, in particular, may end the controversy as to whether borderline personality disorder is in, fact part, of the bipolar spectrum. Such considerations argue for the development of new classification systems, which are based not simply on symptoms but also on neurobiology.
Keywords: bipolar disorder, unipolar depression, borderline personality disorder, post-traumatic stress disorder, neurobiology, MRI