Context Diffusion tensor imaging (DTI) studies in adults with bipolar disorder (BD) indicate altered white matter (WM) in the orbitomedial prefrontal cortex (OMPFC), potentially underlying abnormal prefrontal corticolimbic connectivity and mood dysregulation in BD. Objective To use tract-based spatial statistics (TBSS) to examine WM skeleton (ie, the most compact whole-brain WM) in subjects with BD vs healthy control subjects. Design Cross-sectional, case-control, whole-brain DTI using TBSS. Setting University research institute. Participants Fifty-six individuals, 31 having a DSM-IV diagnosis of BD type I (mean age, 35.9 years [age range, 24-52 years]) and 25 controls (mean age, 29.5 years [age range, 19-52 years]). Main Outcome Measures Fractional anisotropy (FA) longitudinal and radial diffusivities in subjects with BD vs controls (covarying for age) and their relationships with clinical and demographic variables. Results Subjects with BD vs controls had significantly greater FA (t>3.0, P≤.05 corrected) in the left uncinate fasciculus (reduced radial diffusivity distally and increased longitudinal diffusivity centrally), left optic radiation (increased longitudinal diffusivity), and right anterothalamic radiation (no significant diffusivity change). Subjects with BD vs controls had significantly reduced FA (t>3.0, P≤.05 corrected) in the right uncinate fasciculus (greater radial diffusivity). Among subjects with BD, significant negative correlations (P<.01) were found between age and FA in bilateral uncinate fasciculi and in the right anterothalamic radiation, as well as between medication load and FA in the left optic radiation. Decreased FA (P<.01) was observed in the left optic radiation and in the right anterothalamic radiation among subjects with BD taking vs those not taking mood stabilizers, as well as in the left optic radiation among depressed vs remitted subjects with BD. Subjects having BD with vs without lifetime alcohol or other drug abuse had significantly decreased FA in the left uncinate fasciculus. Conclusions To our knowledge, this is the first study to use TBSS to examine WM in subjects with BD. Subjects with BD vs controls showed greater WM FA in the left OMPFC that diminished with age and with alcohol or other drug abuse, as well as reduced WM FA in the right OMPFC. Mood stabilizers and depressed episode reduced WM FA in left-sided sensory visual processing regions among subjects with BD. Abnormal right vs left asymmetry in FA in OMPFC WM among subjects with BD, likely reflecting increased proportions of left-sided longitudinally aligned and right-sided obliquely aligned myelinated fibers, may represent a biologic mechanism for mood dysregulation in BD.

Background-Bipolar disorder is frequently misdiagnosed as major depressive disorder delaying appropriate treatment and worsening outcome for many bipolar individuals. Emotion dysregulation is a core feature of bipolar disorder. Measures of dysfunction in neural systems supporting emotion regulation may therefore help discriminate bipolar from major depressive disorder.

Objective-To examine abnormal patterns of frontal cortical-subcortical activity in response to emotional stimuli in euthymic individuals with bipolar disorder type I in order to identify trait-like, pathophysiologic mechanisms of the disorder. We examined potential confounding effects of total psychotropic medication load and illness variables upon neural abnormalities.Method-We analyzed neural activity in 19 euthymic bipolar and 24 healthy individuals to mild and intense happy, fearful and neutral faces.Results-Relative to healthy individuals, bipolar subjects had significantly increased left striatal activity in response to mild happy faces (p < 0.05, corrected), decreased right dorsolateral prefrontal cortical (DLPFC) activity in response to neutral, mild and intense happy faces, and decreased left DLPFC activity in response to neutral, mild and intense fearful faces (p < 0.05, corrected). Bipolar and healthy individuals did not differ in amygdala activity in response to either emotion. In bipolar individuals, there was no significant association between medication load and abnormal activity in these regions, but a negative relationship between age of illness onset and amygdala activity in response to mild fearful faces (p = 0.007). Relative to those without comorbidities, bipolar individuals with comorbidities showed a trend increase in left striatal activity in response to mild happy faces.Conclusions-Abnormally increased striatal activity in response to potentially rewarding stimuli and decreased DLPFC activity in response to other emotionally salient stimuli may underlie mood instabilities in euthymic bipolar individuals, and are more apparent in those with comorbid diagnoses. No relationship between medication load and abnormal neural activity in bipolar individuals suggests that our findings may reflect pathophysiologic mechanisms of the illness rather than medication confounds. Future studies should examine whether this pattern of abnormal neural activity could distinguish bipolar from unipolar depression. Bipolar disorder is one of the most debilitating illnesses worldwide (1). Bipolar disorder type I, in particular, is characterized by abnormalities in psychosocial and cognitive function as well as emotion and mood regulation that can persist outside of episodes of mania and depression, during remission (2-6), and likely reflect pathophysiologic mechanisms of the illness (7) that are not mood state dependant. The research agenda for DSM-V emphasizes a need to translate basic and clinical neuroscience findings into a new classification system for all psychiatric disorders based upon pathophysiologic and etiological processes (8,9). Examining neural system abnormalities in euthymic individuals with bipolar disorder type I during paradigms specifically designed to measure emotion processing is therefore a first stage toward identifying biomarkers of bipolar disorder that reflect pathophysiologic neural mechanisms of the disorder (10). These, in turn, can then be included in future diagnostic cl...

Background Difficulties in emotion processing and poor social function are common to bipolar disorder (BD) and major depressive disorder (MDD) depression, resulting in many BD depressed individuals being misdiagnosed with MDD. The amygdala is a key region implicated in processing emotionally salient stimuli, including emotional facial expressions. It is unclear, however, whether abnormal amygdala activity during positive and negative emotion processing represents a persistent marker of BD regardless of illness phase or a state marker of depression common or specific to BD and MDD depression. Methods Sixty adults were recruited: 15 depressed with BD type 1 (BDd), 15 depressed with recurrent MDD, 15 with BD in remission (BDr), diagnosed with DSM-IV and Structured Clinical Interview for DSM-IV Research Version criteria; and 15 healthy control subjects (HC). Groups were age- and gender ratio-matched; patient groups were matched for age of illness onset and illness duration; depressed groups were matched for depression severity. The BDd were taking more psychotropic medication than other patient groups. All individuals participated in three separate 3T neuroimaging event-related experiments, where they viewed mild and intense emotional and neutral faces of fear, happiness, or sadness from a standardized series. Results The BDd—relative to HC, BDr, and MDD—showed elevated left amygdala activity to mild and neutral facial expressions in the sad (p < .009) but not other emotion experiments that was not associated with medication. There were no other significant between-group differences in amygdala activity. Conclusions Abnormally elevated left amygdala activity to mild sad and neutral faces might be a depression-specific marker in BD but not MDD, suggesting different pathophysiologic processes for BD versus MDD depression.

BackgroundMajor Depressive Disorder (MDD) is among the most prevalent and disabling medical conditions worldwide. Identification of clinical and biological markers (“biomarkers”) of treatment response could personalize clinical decisions and lead to better outcomes. This paper describes the aims, design, and methods of a discovery study of biomarkers in antidepressant treatment response, conducted by the Canadian Biomarker Integration Network in Depression (CAN-BIND). The CAN-BIND research program investigates and identifies biomarkers that help to predict outcomes in patients with MDD treated with antidepressant medication. The primary objective of this initial study (known as CAN-BIND-1) is to identify individual and integrated neuroimaging, electrophysiological, molecular, and clinical predictors of response to sequential antidepressant monotherapy and adjunctive therapy in MDD.MethodsCAN-BIND-1 is a multisite initiative involving 6 academic health centres working collaboratively with other universities and research centres. In the 16-week protocol, patients with MDD are treated with a first-line antidepressant (escitalopram 10–20 mg/d) that, if clinically warranted after eight weeks, is augmented with an evidence-based, add-on medication (aripiprazole 2–10 mg/d). Comprehensive datasets are obtained using clinical rating scales; behavioural, dimensional, and functioning/quality of life measures; neurocognitive testing; genomic, genetic, and proteomic profiling from blood samples; combined structural and functional magnetic resonance imaging; and electroencephalography. De-identified data from all sites are aggregated within a secure neuroinformatics platform for data integration, management, storage, and analyses. Statistical analyses will include multivariate and machine-learning techniques to identify predictors, moderators, and mediators of treatment response.DiscussionFrom June 2013 to February 2015, a cohort of 134 participants (85 outpatients with MDD and 49 healthy participants) has been evaluated at baseline. The clinical characteristics of this cohort are similar to other studies of MDD. Recruitment at all sites is ongoing to a target sample of 290 participants. CAN-BIND will identify biomarkers of treatment response in MDD through extensive clinical, molecular, and imaging assessments, in order to improve treatment practice and clinical outcomes. It will also create an innovative, robust platform and database for future research.Trial registrationClinicalTrials.gov identifier NCT01655706. Registered July 27, 2012.