LAUSR

To the Editors, In his commentary “Tinkering at the margins”,1 Chanen maintains that the distinction between borderline personality disorder (BPD) and bipolar disorder (BD) can be readily determined in “daytoday clinical practice” using current diagnostic criteria. It is common, however, for it to be argued that their differentiation is difficult. We suggest that there are two reasons for such differentiation difficulties. Firstly, there is a need to proceed beyond clinical syndrome criteria and enrich them with condition correlates. For example, in recent studies and reviews, samples of those with a BPD were able to be differentiated at levels in excess of 90% from those with a BP condition by a small set of variables including (i) female gender, (ii) childhood sexual abuse, (iii) depersonalization in childhood, (iv) sensitivity to criticism, (v) relationship difficulties, (vi) absence of a bipolar family history and (vi) a higher rate of deliberate selfharm and suicidal attempts.2 It was also noted that the mood states in those with BPD are marked more by anger than by euphoria, that the depressive episodes tend to be nonmelancholic as against the likelihood of melancholic episodes in those with a BP condition, that there is a greater likelihood of a family history of impulse disorders in those with a BPD, and that those with a BPD evolve into the disorder in adolescence and adulthood rather than showing the “trend break” generally evidenced by those with a bipolar condition (i.e. a new state of categorical mood swings commencing rather than evolving). The second reason for differentiation difficulties is that we, as clinicians, tend to operate to a rule of parsimony (i.e. which condition is “the diagnosis”?), while studies have identified that 10%20% of those with BP or BPD also have the other condition. In our paper “Defining permeable borders: you say bipolar, I say borderline!” we were, however, attempting more to clarify the interface between BPD and BD, rather than to identify those characteristics of these disorders that were unmistakably different. For example, it is clinically relatively easy to distinguish severe mania in BD from the highly aroused emotive states of BPD. Our intention was to explore the boundaries of these disorders in an attempt to identify their differences and similarities. With this in mind, the constructs of “projective identification” and “noxious sense of self” are meaningful because they offer fundamental differences in these disorders which are reflected in clinical presentations. While Chanen is correct that sexual and other forms of abuse occur in association with BD, the prominence of such abuse in BPD is so pervasive that many observers have suggested BPD would be better considered a form of complex posttraumatic stress disorder. Chanen mentions the similarities of psychosis in BPD to a number of other psychiatric disorders. We agree that some elements of psychosis (auditory hallucinations) in BPD are similar to those observed in other disorders; however, the scientific evidence regarding the characteristics of psychosis in BPD is still lacking in clarity and is generally different in form and content from that seen in BD.3 In addition, we agree that there is insufficient scientific evidence that antipsychotic medications are often of limited efficacy in the psychosis associated with BPD, but our clinical experience and that of many others supports this contention. Studies of the life history of BPD support our contention that the prognosis for BPD is generally better than that for BD. It is true that patients with BPD are often left with residual difficulties in interpersonal interactions, but their emotional dysregulation and quality of life tend to improve with advancing age. In conclusion, we suggest that Chanen has overinterpreted the content of our paper – which sought, in essence, to clarify the interface between two complex groups of disorders.