Wednesday 5 April 2017
New diagnostic model for psychiatric disorders proposed
University of Otago researcher Associate Professor Martin Sellbom is part of a group of 50 leading international
psychologists and psychiatrists who have put forward a new, evidence-based, system for classifying mental health
disorders.
The researchers hope that their recommendations will lead to a paradigm-shift in how mental illnesses are classified and
diagnosed. Their study appears in the American Psychological Association’s Journal of Abnormal Psychology.
Their new Hierarchical Taxonomy of Psychopathology (HiTOP) addresses limitations to the reliability and validity of
traditional models such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the American Psychiatric
Association’s (APA) authoritative handbook used by clinicians and researchers around the world to diagnose and treat
mental disorders.
They hope HiTOP will advance research efforts and improve clinical outcomes related to the causes and treatments of
mental disorders.
Associate Professor Sellbom, who is a member of Otago’s Department of Psychology, says HiTOP represents a new system for
the classification of mental health problems that is rooted completely in cumulative scientific knowledge, unlike the
current DSM-5 and the International Statistical Classification of Diseases and Related Health Problems (ICD-10).
“The DSM-5 relies on ‘categorical’ diagnoses which are assigned if a person has X out of Y symptoms, with no actual
scientific basis for a qualitative change when you reach X symptoms. People with fewer symptoms are often just as
impaired, but are considered to have no diagnosis,” he says.
Instead, HiTOP relies on dimensional (or continuous) representations of mental health problems, which allows for a
better consideration of severity, and also recognise the existence of significant problems that don’t currently meet
full DSM diagnostic thresholds, he says.
“HiTOP organises mental health problems hierarchically, which allows for a better understanding of which causes
contribute to what these problems have in common.”
A major advantage of the hierarchical model is its use of empirical evidence to classify disorders, a change from the
DSM’s tendency to group disorders based partly on clinical assumptions about which disorders seem to go together. For
instance, several of the anxiety disorders of the DSM-5 have been grouped together based on content themes rather than
their scientific associations, he says.
“For instance, Major Depressive Disorder and Generalised Anxiety Disorder have a far more significant overlap than do
Generalised Anxiety Disorder and the other so-called anxiety disorders, such as social anxiety disorder or specific
phobias. Such scientifically based groupings link classification to shared underlying causes and therefore better
targeted treatments than the current arbitrary thematic groups.”
The researchers used several large epidemiological surveys in the United States, Australia, the Netherlands, and other
countries to gather data about how the most common forms of psychopathology – such as depression, anxiety, substance
abuse and personality disorder – are related.
The consortium’s paper is titled “The Hierarchical Taxonomy of Psychopathology (HiTOP): A Dimensional Alternative to
Traditional Nosologies” and can be viewed here.
Professor Terrie Moffitt, Associate Director of the internationally renowned Dunedin Study, is also a co-author on the
paper.