The NIMH Research Domain Criteria (RDoC) project is intended to further a long-range goal of contributing to diagnostic systems as informed by research on genetics, neuroscience, and behavior. The Request for Applications to which we are responding encourages applications to study RDoC Constructs that cut across traditional diagnostic categories. Because RDoC Constructs are theoretical entities instantiated by behavioral and neurobiologic assessments, their validation (in the absence of a known gold standard) requires an empirical framework. This proposal seeks to apply such a framework to RDoC Constructs of the Positive Valence Systems. We will apply an updated version of the validation system proposed by Robins and Guze, which has been used for many decades as a tool for validating psychiatric constructs. We will focus on four of the five questions asked by this method: Is the Construct coherent? Is it familial? Is it associated with neurobiologic measures? Is it stable over time? Our work will answer the first three questions and will set the stage for a longitudinal study to answer the fourth. In the RDoC spirit, we will take an agnostic approach regarding nosology by ascertaining families having a child with any psychiatric disorder through referrals to our general child psychiatry clinic. We will also sample non-psychiatric comparison subjects from the community to assure that we have a wide range of scores on the RDoC Constructs represented in our study and to assess the clinical significance of Construct measures. We are adopting a clinic-based approach with appropriately matched community controls because, although the RDoC Domains are not intended to define particular disorders, any study of these domains should be more powerful when studying a sample enriched for individuals with extreme values on these traits (i.e., those with or without psychiatric disorders).2 As a consequence, we can simultaneously evaluate RDoC constructs and the predominant traditionally defined childhood psychiatric disorders in one study. Our approach is also clearly relevant to the target population of NIMH and the RDoC initiative; i.e., children and adults exhibiting impairing psychiatric symptoms. Using this sample, we will accomplish the following Specific Aims: 1) Determine if Constructs in the Positive Valence System Domains proposed by the NIMH Working Groups are homogenous theoretical Constructs; 2) Determine if Positive Valence System Constructs are familial; 3) Determine if Positive Valence System Constructs predict psychopathology and impairment; 4) Determine if Positive Valence System Constructs are associated with Construct candidate genes, with recently identified genome-wide significant cross-disorder candidate genes, and with cross-disorder polygenic scores; and 5) Establish a database of enrolled families and maintain annual contact with them to ensure the viability of longitudinal follow-up analyses.
This proposal seeks to apply an empirical framework to validating a recently proposed set of biological bases for behavior, collectively known as the Research Domain Criteria. We aim to identify the most critical or essential features of proposed assessments for these new criteria, as well as the genes that relate to these constructs. In so doing, we will enable fundamental changes to be made to the current psychiatric diagnostic system so that these disorders can be classified by their underlying causes (which, in turn, should suggest more specific treatment avenues) rather than by ambiguous clusters of symptoms and behaviors.
