This paper provides an overview of the major studies of bipolar affective disorder (BAD) and borderline personality disorder (BPD), and assesses whether the disorders might be better understood as variants of the same basic disorder. There is a shortage of research that delineates the features of both disorders within their representative samples. As a consequence the symptomatic overlap of the disorders, detected by categorical assessment instruments, is often misconstrued as an indication of the disorders' high rates of comorbidity (up to 81%).

In paying particular attention to features of both disorders, eg. affective instability and impulsivity, the paper provides evidence that BPD attenuates bipolar disorder along the spectrum of affective disorders, from non-classical bipolar presentation through to severe BAD with borderline features. The paper cites clinical, research and pharmacologic support of the contention that BPD, rather than representing a distinct disorder, is merely an attenuation of Axis I disorders, most especially bipolar affective disorder. Borderline personality is evident across the bipolar spectrum and exacerbates symptomatology and leads to poorer recovery prognosis.