Developmental and Environmental Aspects
While RDoC calls for the study of circuit-based functional dimensions as studied across multiple units of analysis, two additional aspects represent equally important elements of the RDoC framework: (1) neurodevelopmental trajectories and (2) interactions with the environment. The intent is that the RDoC matrix will promote a systematic focus on development and the environment – as well as with their mutual interactions – and their individual and interacting relationships to specific circuits and functions.
- Development. Understanding developmental trajectories across various phases of the life span represents a critical consideration that is implicit to the RDoC framework, and might be considered as a third dimension in the matrix. The types of constructs typically found in the literature on human neurodevelopment are (not coincidentally) similar to several RDoC domains, and many areas of the child psychopathology literature (e.g., reward sensitivity, cognitive and emotional dysregulation, behavioral inhibition) serve as a more compatible model for a dimensionally-based approach compared to the highly specified categories of adult psychopathology. A more comprehensive understanding of the trajectories that lead to disorders, particularly in the context of quantified measures that can validly identify pre-symptomatic dysfunction, is obviously essential to early prevention efforts.
- Because the intent is to liberate investigators to pursue the most promising leads for a given question, formal developmental guidance is not provided in the matrix. Some neurodevelopmental milestones may be relatively time-limited (e.g., the onset of walking), others are somewhat more extended (e.g., puberty), and factors such as changes across the adult life course span decades. Thus, investigators must be free to define the most appropriate developmental events and time frame for their research question.
- Four brief examples of life-span questions that could be addressed within the RDoC framework:
- Further explicate the longitudinal course of adolescent brain maturation and synaptic pruning to identify genes and circuit development factors associated with departures from normal developmental functioning, and points in prodromal stages where intervention might particularly be targeted to prevent onset of psychosis;
- Evaluate the extent to which the recruitment of additional cortical areas during task performance or emotional challenge in elderly subjects predicts resilience against onset or deterioration of course in mental disorders;
- Generate improved explication of the construct of cognitive control (or effortful control), relative to disentangling current controversies regarding ADHD, conduct disorder, and other externalizing disorders of childhood;
- Specify the mechanisms regarding developmental changes in systems for fear and distress across puberty (including the effects of the social environment), that could explain the peak onset of internalizing symptoms in adolescence and their correlation with puberty.
- Environment. It is now widely accepted that most mental illnesses result from maladaptive maturation of the nervous system including its interaction with the wide variety of external influences beginning at conception. The social and physical environment comprises sources of both risk and protection for many different disorders occurring at all points along the life span, and methods for studying phenomena such as gene expression, neural plasticity, and various types of learning are rapidly advancing. As with developmental aspects, environmental influences may thus be considered as another critical element of the RDoC matrix. Particular environmental stressors, such as early child abuse, may increase risk for a wide variety of disorders. Environmental effects must frequently be studied bidirectionally; for example, an individual’s behavior affects his/her social environment (e.g., family or friends), which in turns affects the nature of others’ behavior toward the individual. Thus, it is hoped that a research program organized around the relevant circuit-based dimensions that are affected, independent of a particular disorder, will accelerate knowledge regarding such environmental influences along the entire range of analysis from genes to behavior.