HOUSTON – A multidimensional framework being developed by the National Institute of Mental Health is poised to bring the understanding of neuropsychiatric disorders up to par conceptually with the insight being achieved in most other medical disciplines, according to Dr. Thomas Insel.
In contrast to current diagnostic constructs that rely on categorical labels based on signs and symptoms alone, the Research Domain Criteria (RDoC) integrate dimensions of observable behavior with neurobiologic measures and genetics, said Dr. Insel, director of the National Institute of Mental Health. The experimental system will "cut across traditional definitions of mental disorders" by assessing basic dimensions of functioning, such as fear circuitry and working memory, across these multiple units of analysis, he said. While the concept itself is not new – most medical disciplines integrate multiple sources of information, such as biomarkers and imaging, into their diagnostic tool kits – its application to psychiatry is revolutionary, he said.
Dr. Thomas Insel
"Think about it. We don’t use the word ‘cure’ in psychiatry," yet the term is part of the lexicon of nearly every other medical specialty, Dr. Insel said in a plenary presentation at the annual meeting of the American College of Psychiatrists. "The reality is, for most mental illnesses, the etiology is unknown, prediction is poor, detection is late, diagnosis is by observation, prevention is not well developed, and treatment is trial and error."
And while most psychiatrists have seen spectacular individual successes and have experienced the satisfaction of helping people in fundamental ways, "on population-based measures, the dial has not moved much, and when it has moved, the movement has been in the wrong direction, as evidenced by the increased prevalence and increases in associated morbidity and mortality," Dr. Insel said. This is incongruous with the extraordinary advances in biomedical research that have transformed our understanding of so many diseases over the past 50 years, he said. "No such advances have been made in the diseases that we treat, such as major depression, schizophrenia, bipolar disorder, eating disorders, or [attention-deficit/hyperactivity disorder] in children."
The public health implications linked to this lack of advancement are staggering, Dr. Insel said. "The World Health Organization's most recent estimate is that mental health disorders are the largest source of disability from all medical causes, a major cause of death, and one of the major drivers of health care costs from within and outside the system," he said, noting that the estimated direct and indirect costs of mental disorders are more than $317 billion annually.
"What we’ve come to realize is that part of the reason we have not made significant progress is because we haven’t thought about these disorders in the right way," Dr. Insel stressed. "Our focus in thinking about serious mental illness has historically come from the standpoint of these being mental or behavioral problems requiring mental or behavioral interventions."
Such a mind-set suggests that focusing on observable signs and symptoms exclusively will lead to a precise diagnosis, although experience suggests otherwise, Dr. Insel said. "The lesson from other areas of medicine is that a diagnosis that relies solely on manifest symptoms is not the best guide to choosing the most effective treatment." This is because symptom-focused diagnostic labels, such as depression or schizophrenia, frequently belie heterogeneous disorders that defy such narrow classification, he said.
Neuroscientific research during the past decade has determined that mental disorders are brain and developmental disorders that result from complex genetic risk plus experiential factors, Dr. Insel explained. As such, the consideration of all of the various factors will enable precise diagnoses and prediction of treatment response. "We are talking about a completely different way of approaching these illnesses that offers real hope for transforming the statistics and moving the dial."
The much-heralded and occasionally controversial move to the DSM-5 is among the pioneering efforts to reflect this new understanding. The goal of the DSM-5 is to move beyond the signs and symptoms classification of mental illness to incorporate biologic measures, according to Dr. David J. Kupfer, the Thomas Detre Professor of Psychiatry at the University of Pittsburgh and chair of the DSM-5 Task Force. "The DSM-5 is intended to be a living document with recommendations that are guided by research evidence as it evolves," he said in a plenary presentation at the meeting. It will incorporate dimensional concepts, including measurement of distress, disability, and severity; the development of the various illnesses across the life span; and new knowledge on genetic and environmental risk factors and prevention, he said.
"The reality is, for most mental illnesses, the etiology is unknown, prediction is poor, detection is late, diagnosis is by observation, prevention is not well developed, and treatment is trial and error."