Objective and biological markers in bipolar spectrum presentations

INTRODUCTION

Subthreshold presentations of bipolarity (BSPs) pose a diagnostic conundrum, in terms of whether they should be conceptualized and treated similarly as traditionally defined bipolar disorders (BD). While it has been argued that BSPs are on a pathophysiologic continuum with traditionally defined BDs, there has been limited examination of biological and objective markers in these presentations to validate this assertion. Areas covered: The authors review studies examining genetic, neurobiological, cognitive and peripheral markers in BSPs, encompassing clinical and non-clinical populations with subthreshold hypo/manic symptoms. Results are placed in the context of previously identified markers in traditionally defined BDs. Expert commentary: There have been few studies of objective and biological markers in subthreshold presentations of BD, and results are mixed. While abnormalities in brain structure/functioning, peripheral inflammatory, and cognitive markers have been reported, it is unclear whether these findings are specific to BD or indicative of broad affective pathology. However, some studies suggest that increased sensitivity to reward and positive stimuli are shared between subthreshold and traditionally defined BDs, and may represent a point of departure from unipolar major depression. Further examination of such markers may improve understanding of subthreshold bipolar presentations, and provide guidance in terms of therapeutic strategies.

Validation of the "rule of three", the "red sign" and temperament as behavioral markers of bipolar spectrum disorders in a large sample

BACKGROUND

Akiskal proposed the "rule of three" for behavioral indicators with high specificity for bipolarity in patients with major depression episodes. We evaluated these distinctive behaviors in controls and subjects with major depression or bipolar disorder.

METHODS

data was collected in the BRAINSTEP project with questions on general behaviors, style and talents. Univariate analysis was first conducted in 36,742 subjects and confirmatory multivariate analysis in further 34,505 subjects (22% with a mood disorder). Odds ratios were calculated adjusting for age.

RESULTS

Univariate analysis showed that 29 behavioral markers differentiated bipolar subjects from those with unipolar depression. The most robust differences in those with bipolarity (ORs >4) were ≥3 religion changes, ≥3 marriages, cheating the partner regularly, having ≥60 lifetime sexual partners, pathological love, heavy cursing, speaking ≥3 foreign languages, having ≥2 apparent tattoos, circadian dysregulation and high debts. Most behaviors were expressed in a minority of patients (usually around 5-30%) and usually the "rule of three" was the best numerical marker to distinguish those with bipolarity. However, multivariate analysis confirmed 11 of these markers for differentiating bipolar disorder from unipolar depression (reversed circadian rhythm and high debts for both genders, ≥3 provoked car accidents and talent for poetry in men, and frequent book reading, ≥3 religion changes, ≥60 sexual partners, pathological love ≥2 times, heavy cursing and extravagant dressing style in women).

LIMITATIONS

Self-report data collection only.

CONCLUSIONS

These behavioral markers should alert the clinician to perform a thorough investigation of bipolarity in patients presenting with a depressive episode.

Bipolar and borderline patients display differential patterns of functional connectivity among resting state networks

Bipolar disorder (BD) and borderline personality (BPD) disorder share clinical features such as emotional lability and poor interpersonal functioning but the course of illness and treatment differs in these groups, which suggests that the underlying neurobiology of BD and BPD is likely to be different. Understanding the neural mechanisms behind the pathophysiology of BD and BPD will facilitate accurate diagnosis and inform the administration of targeted treatment. Since deficits in social cognition or emotion regulation or in the self-referential processing system can give rise to these clinical features, and impairment in these domains have been observed in both patient groups, functional connectivity within and between networks subserving these processes during resting was investigated using functional magnetic resonance imaging. Data were acquired from 16 patients with BD, 14 patients with BPD, and 13 healthy controls (HC) and functional connectivity strength was correlated with scores using the Difficulties in Emotion Regulation Scale. Functional network connectivity (FNC) patterns differentiated BD and BPD patients from HC. In BD, FNC was increased while in BPD it was decreased. In BD impaired FNC was evident primarily among networks involved in self-referential processing while in BPD it also involved the emotion regulatory network. Impaired FNC displayed an association with impulsivity in BPD and emotional clarity and emotional awareness in BD. This study shows that BD and BPD can perhaps be differentiated using resting state FNC approach and that the neural mechanisms underpinning overlapping symptoms discernibly differ between the groups. These findings provide a potential platform for elucidating the targeted effects of psychological interventions in both disorders.