Although the Research Domain Criteria project (RDoC) is not particularly new (the description of it on the NIMH website is dated June 2011 and it’s been on my reading list for at least a year), there has been a lot of attention drawn to it recently. This is partly because the DSM-5, the new psychiatric diagnostic handbook, is due to be published on May 18th, prompting Thomas Insel, director of the National Institute for Mental Health (NIMH), to recently write about the necessary next steps in mental health research (see here and here). I’m sure many others (for example The Neurocritic) have written about this recently. Having finally gotten around to reading about RDoC on the NIMH website myself, I wanted to briefly summarise what it is and why it’s brilliant. If you haven’t heard of RDoC or keep meaning to look it up, this is for you.
The RDoC project is a framework for thinking about and researching all aspects of human psychopathology/mental health, without confining the research to existing diagnostic labels. The DSM-5 is the best thing we currently have for the purpose of clinical assessments and diagnosis, in the hope of trying to treat and improve the lives of people with mental health difficulties. But research suggests that it isn’t good enough.
In reality, mental health conditions overlap greatly, both in terms of clinical presentation, associated features (e.g. cognitive difficulties) and in terms of apparently non-specific risk factors (e.g. many genetic variants have now been shown to play a role in more than one condition (e.g. schizophrenia, autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), all previously thought to be quite distinct conditions)). Even within a diagnostic category, there is a lot of variability in severity and also, you don’t need a diagnosis to have problems; symptoms below diagnostic thresholds often cause difficulties for affected people. It has become clear that mental health problems are not binary. Instead, there appears to be a continuous distribution of mental health difficulties, ranging from none to very severe.
The RDoC framework is about cutting across these diagnostic labels and looking at the underlying dimensions of behaviours and measures of neurobiology. The idea is that recruiting participants to a study on mental health based on their diagnoses and then trying to determine how they differ from “healthy” controls in order to inform research on diagnoses, is actually a little circular. The alternative approach, suggested by the RDoC framework, is to recruit participants with a range of related problems (e.g. all types of mood disorders) and look within this group.
(Example of the 2 main dimensions of the RDoC Framework)
The framework divides up mental health into a list of constructs (such as ‘Responses to potential harm (Anxiety)’, ‘Reward Learning’, ‘Cognitive Control’ or ‘Social Communication’) within more general domains (e.g. Cognitive Systems). It then divides research approaches into units of analysis (e.g. Genes, Molecules, Cells, Observed Behaviour etc.). Two other dimensions are ‘Developmental Aspects’ (how these constructs change over time) and ‘Environmental Aspects’ (how the environment affects and interacts with the constructs).
The hope is that considering mental health in terms of these dimensions rather than diagnoses, will serve as a research framework for improving our understanding of mental health and creating better diagnostic categories for the future. This framework seems to me a much more valuable way of doing research in this area. It reminds me of a great blog post by Dorothy Bishop from 2010, in which she argued that neurodevelopmental problems should be considered on a number of developmental dimensions, rather than as discrete clusters of difficulties (i.e. diagnostic categories). I was very inspired by this way of thinking when I first started my PhD and so I think it’s great to see that the NIMH is encouraging researchers in mental health to adopt this way of thinking.