Trajectories of Treatment Response as Window Into the Heterogeneity of Psychosis: a Longitudinal Multimodal Imaging Study

Overview

Psychosis is a heterogeneous disorder and present treatment only works for a limited number of patients. In order to identify new therapeutic targets, this study will longitudinally characterize the underlying pathologies in those with poor treatment response using complimentary brain imaging modalities.

Schizophrenia is a heterogeneous disorder that likely involves multiple underlying pathological mechanisms, which has plagued attempts to identify rational therapeutic targets. All available antipsychotic drugs (APD) are dopamine receptor antagonists, but clinical response is variable, with a third of patients being partial responders, and a third non-responders. Arguably, those who respond well to APD have primarily dopaminergic abnormalities but it is imperative to also characterize the specific underlying pathologies in those with poor response in order to unravel the heterogeneity of psychosis and effectively develop new treatments. The investigators propose to longitudinally follow treatment response to APD for eight months in medication-naïve first episode psychosis (FEP) subjects using complementary brain imaging techniques. The investigators have already identified provisional markers for several different pathophysiological mechanisms underlying psychosis, including abnormalities in glutamate, brain connectivity, and neurodevelopment that they can track with brain imaging. In addition, the investigators propose to study the changes that occur in the brain in early compared to delayed treatment responders and changes that occur over time in response to treatment. By characterizing treatment trajectories and their relationship to baseline pathophysiologic alterations, the investigators will further complement their mechanistic understanding of the heterogeneity of psychosis. The investigators propose to study 117 well-characterized FEP subjects who are medication naïve and treat them with the most frequently used APD for 32 weeks. The investigators will follow a rigorous longitudinal design to capture treatment response whereby those without an adequate response after 16 weeks of treatment will be switched to another APD for 16 weeks. All patients will be scanned four times: at baseline and after 6, 16, and 32 weeks of treatment. The investigators will use (1) proton MR Spectroscopy (MRS), (2) task and resting state functional MRI and (3) MRI and diffusion weighted imaging (DWI) to measure brain biochemistry, function and structure. Using several imaging modalities has the potential to interrogate different neurobiological aspects of treatment response and will offer greater opportunities for clustering the patterns and combinations of the underlying pathologies in those with poor response. Deconstructing the heterogeneity of psychosis has broad implications for the identification of specific targets for drug development, and to lay the groundwork needed to conduct therapeutic trials on patients characterized by their specific underlying psychopathology.

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