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Abstracts
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doi:10.1016/j.schres.2014.09.067
Biomarkers of vulnerability and progression in the psychosis prodrome Tyrone D. Cannon1 Department of Psychology, Yale University, United States; Department of Psychiatry, Yale University, United States 1 On behalf of the North American Prodrome Longitudinal Study (NAPLS) Consortium. E-mail:
[email protected] Identification of the fundamental mechanisms underlying onset of psychosis is critical for the development of targeted pre-emptive interventions. This talk presented findings on clinical risk prediction algorithms as well as biomarkers assessed longitudinally in youth at clinical high-risk for psychosis as part of the second phase of the North American Prodrome Longitudinal Study (NAPLS2) (Addington et al., 2012). The study cohort consists of 765 clinical high-risk (CHR) participants and 260 healthy control subjects. The primary outcome was conversion to psychosis over 2 years from initial evaluation. Participants were evaluated with structural MRI, electrophysiology (mismatch negativity [MMN], auditory P300), and cortisol assays at baseline and at 12 months or at conversion to psychosis. Smaller subgroups were evaluated with functional MRI (resting state, verbal working memory, associative learning, emotion processing) and plasma analytes (indexing inflammatory and oxidative stress markers) at baseline. Multivariate models incorporating risk factors from clinical, demographic, neurocognitive, and psychosocial assessments achieved high levels of predictive accuracy when applied to individuals who meet criteria for a prodromal risk syndrome. A risk calculator was created that can be used to scale the risk for newly ascertained cases based on this set of predictors (Cannon, 2014). With respect to biomarkers, at risk individuals who converted to psychosis showed elevated levels of cortisol (Walker et al., 2013) and pro-inflammatory cytokines (Perkins et al., in press), as well as lower MMN and P300 amplitude (Mathalon et al., 2014) and disrupted resting state thalamo-cortical functional connectivity (Anticevic et al., 2014) at baseline, compared to those who do not. Further, converters showed a steeper rate of gray matter reduction, most prominent in prefrontal cortex that in turn was predicted by higher levels of cortisol and inflammatory markers as well as by lower MMN amplitude at baseline (Cannon et al., in press). Each biomarker was a significant predictor of psychosis on its own, and several improved predictions over and above the level achieved by the clinical, demographic, and cognitive algorithm (Cannon, 2014). Microglia, resident immune cells in the brain, have recently been discovered to influence synaptic plasticity in health (Schafer et al., 2013; Zhang et al., 2014) and impair plasticity in disease (Takano et al., 2014). Processes that modulate microglial activation may represent convergent mechanisms that influence brain dysconnectivity and risk for onset of psychosis. Inflammatory markers are elevated in postmortem neural tissue from patients with schizophrenia (Catts et al., 2014; Fillman et al., 2013; Fung et al., 2014; Rao et al., 2013) and these same markers are associated with microglialmediated synaptic pruning and dendritic retraction in animal models (Milatovic et al., 2011; Schafer et al., 2013), thus, providing a potential mechanism for the reduced neuropil and disrupted functional connectivity seen in patients (Glausier and Lewis, 2013; Selemon and Goldman-Rakic, 1999; Selemon et al., 1998). Although prenatal neuroinflammatory processes could “program” for vulnerability (Meyer, 2013), subsequent exposure to stress, infection, autoimmune processes and/or synaptic pruning during adolescent brain development represents influences more proximal to psychosis onset (Frick et al., 2013; Glausier and Lewis, 2013; McGlashan and Hoffman, 2000; Meyer, 2013). Future work is encouraged to target these
mechanisms in longitudinal studies of CHR subjects; results will help to identify targets for preventative intervention.
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doi:10.1016/j.schres.2014.09.068
Dopamine dysfunction in schizophrenia Anissa Abi-Dargham Department of Psychiatry, Columbia University, New York State Psychiatric Institute, NY, USA E-mail:
[email protected]