How will the RDoC matrix actually function as a classification system for experimental purposes? For perspective, it may be pointed out that the current system imposes three constraints upon the independent variable (ie, group classification) in psychiatric studies: first, symptoms are the unit of analysis that must be utilized; second, find more particular constellations of symptoms

must be employed (ie, the DSM poly thetic Inhibitors,research,lifescience,medical criteria or their ICD equivalents); and third, the symptoms must be employed (with rare exceptions) simply to render a binary, diagnosis present/absent decision rather than being quantified in any way. RDoC is intended to free investigators from these constraints. An element from any unit of analysis may be the independent variable. In a study of working memory, performance on a working memory task could be the independent variable (possibly stratified by particular genetic polymorphisms), and activation of relevant working memory areas (as measured by fMRI) Inhibitors,research,lifescience,medical and real-world functional capacity might be dependent variables. As another example, patients presenting with internalizing (mood or anxiety) disorders might be classified along a dimension of their overall symptom reports of distress (but independent of DSM diagnosis), and fear circuit activation Inhibitors,research,lifescience,medical in some relevant task (eg, imagery, film clips) might be assessed in order to test the hypotheses

that increasing severity and/or chronicity of distress are associated with hyporeactivity in fear activation circuits. In each case, the independent variable cannot be assigned until after the experimental procedures are conducted; because the independent variable is dimensional, however, this does not necessarily pose problems in statistical Inhibitors,research,lifescience,medical power or matching subjects in groups. As these examples imply, the choice of which units of analysis to use as independent and dependent variables depends upon

the research question. Particularly in the early phases of studies using the RDoC approach, it may be heuristic for investigators to report the number of participants in study samples who meet diagnostic criteria for various DSM primary diagnoses in order to facilitate comparisons Inhibitors,research,lifescience,medical with traditional and RDoC classification. However, it should be noted that one major emphasis of Strategic Aim 1.4 is to delineate the entire range of a particular dimension, notably including Cediranib (AZD2171) patients who fall short of traditional diagnostic criteria or who may have an NOS (Not Otherwise Specified) diagnosis. Thus, including only those subjects who meet criteria for designated DSM/ICD disorders (even if more than one) is not a wholly satisfactory approach in the RDoC perspective. One of the inherent problems with the categorical approach is that, in spite of the acknowledged heterogeneity that is apparent in virtually all clinical diagnoses, the consequent analysis implicitly involves the notion of a unitary entity that has a “point” Expected Value and “normal” variance on any given measure.