To assess the prevalence of bipolarity and its impact on clinical course, psychiatric consultants’ diagnostic impressions and respective treatment outcomes were examined for patients with depression who were treated in a collaborative care model (CoCM) of psychiatric consultation.
Electronic records for 1,476 patients were reviewed for the presence of a mood disorder, which yielded 641 patients with complete data on several measures: the Composite International Diagnostic Interview, version 3.0 (CIDI); a questionnaire eliciting data on non-mania-related markers of bipolar disorder (family history, age of onset, course of illness, response to treatment); consultants’ diagnostic impressions; and Patient Health Questionnaire-9 (PHQ-9) scores before and after consultation.
Of referred patients, 97% were screened for bipolar disorder. A smooth distribution of scores on the CIDI was observed. Patients were divided into four groups on the basis of their CIDI scores (≥7, positive, or <7, negative) and on the consultant's recorded Impression (positive or negative for bipolarity). Of the study sample, 21% were CIDI positive (≥7), and 35% were Impression positive (sufficient bipolarity to guide treatment recommendations). All groups demonstrated equivalent decreases in PHQ-9 scores in the 6 months since consultation, including the potentially overdiagnosed group (CIDI negative, impression positive), which comprised 22% of the study sample.
Universal screening for bipolarity in primary care is feasible in CoCM programs. Interpreting the data dimensionally is logical on the basis of the smooth distribution of CIDI scores. Such screening will yield high rates of bipolar disorder, much higher than previously reported. Offering treatment recommendations based on an impression of bipolarity to patients with negative CIDI results (<7) was not associated with outcomes worse than experienced by all other consultation patients. Multiple explanations of the latter finding are possible, warranting additional study.