We address the following questions: (i) What is the frequency of each disorder when the other is present? (ii) Is the level of co-occurrence elevated? That is, is the prevalence of BPD significantly higher in patients with bipolar disorder than in other psychiatric disorders? (iii) Is BPD the most common personality disorder in bipolar patients or are other personality disorders Inhibitors,research,lifescience,medical more frequent? Methodological issues in personality disorder assessment Any review of

a topic involving personality disorders needs to consider assessment methodology, because assessment issues can have a significant impact on the findings. In short, there should be some consideration of the who, what, and when of personality disorder assessment.To be sure, these are also issues in the evaluation of Axis I disorders, though they have not been studied as much as they have been studied in the personality Inhibitors,research,lifescience,medical disorder field. Who should be questioned when assessing personality disorders-the target individual or someone who knows the target individual well? The evaluation

of personality disorders presents special problems that may require the use of informants. In contrast to the symptoms of major Axis I disorders, the defining features of personality disorders are based on an extended longitudinal perspective of how individuals act in different situations, how they Inhibitors,research,lifescience,medical perceive and

interact with a constantly changing environment, and the perceived reasonableness of their behaviors and cognitions. Only a minority of the personality disorder criteria are discrete, easily enumerated behaviors. For any individual to describe their normal personality they Inhibitors,research,lifescience,medical must be somewhat introspective and aware of the effect their attitudes and behaviors Inhibitors,research,lifescience,medical have on others. But insight is the very thing usually lacking in individuals with a personality disorder. DSM-IV notes that the characteristics defining a personality disorder may not be considered problematic by the affected individual (ie, Selleck EPZ5676 ego-syntonic) and suggests that information be obtained from informants. Research comparing patient and informant report of personality pathology has found marked disagreement between the two sources of information.36-39 Only one of the why studies examining the frequency of personality disorders in patients with bipolar disorder examined the impact of informant assessment on the rates of personality disorder diagnoses.40 Peselow et al40 presented personality disorder rates based on independent patient and informant interviews, and we have included in Table I the results based on the patient information in order to be consistent with other studies. Table I Methods of studies of the frequency of borderline personality disorder in individuals with bipolar disorder.