ABSTRACT: Administrative Supplements for NIMH Grants to Expand Suicide Research Suicide is among the top leading causes of death in the US; individuals with schizophrenia (Sz) have a lifetime risk of more than tenfold that of the general population. Suicidal ideation and behavior (SIB) are prevalent also in clinical risk states for schizophrenia, in teens and young adults at increased clinical high risk (CHR) for Sz and related psychotic disorders, based on attenuated psychotic symptoms (APS). In CHR cohorts, lifetime prevalence is ~77% for suicidal ideation and ~20% for suicidal behavior and attempts. Base rates for suicide by death after ascertainment is ~1% within a few years. Despite the clear public health problem of SIB in CHR teens and young adults, there is a clear gap in our understanding of their associated mechanisms and neural substrates, and their demographic, symptom and clinical correlates. It is important to gain a better understanding of SIB in CHR individuals in order to extend prevention efforts for CHR individuals beyond prevention of psychosis and poor functional outcome to include suicide prevention as well. This proposal is an administrative supplement submitted in response to NOT-MH-19-026 Administrative Supplements for NIMH Grants to Expand Suicide Research, for the parent R01 of “Thought disorder and social cognition in clinical risk states for schizophrenia” (end 2021). It capitalizes on the parent R01's prospective cohort that includes data across multiple levels of analysis, including behavior (language, social cognition, symptoms) and circuits (brain structure and function), as well as data on SIB collected for purposes of safety, using the PhenX toolkit measure of the Columbia Suicide Severity Rating Scale (C-SSRS). Therefore, this supplement does not entail the addition of any new measures. It is expected there will be data on 90 CHR, 25 Sz, and 25 healthy individuals by mid-2020 amenable for analysis (preliminary data now includes 30 CHR). This supplement adds a new specific aim relevant to suicide risk, namely to identify linguistic/cognitive biomarkers, symptom/demographic correlates and neural substrates of C-SSRS SIB in CHR individuals using advanced analytic methods, including natural language processing, machine learning, penalized regression, and sparse modeling. The work proposed is within the scope of the parent R01 as it entails the application of similar advanced analytic methods to the same dataset, to understand mechanisms of key clinical features in a young at-risk cohort (parent R01: psychosis risk: supplement: suicide risk). It is hypothesized that SIB will be associated in CHR individuals with greater use of words with negative emotional content and greater self-focus in language (use of personal pronouns), social cognitive deficits, depression, motivational deficits, gray matter reduction and abnormal resting connectivity.