DSM-5: Diagnosis Trouble

The controversy surrounding the impending release of the DSM-5 may have spurred on one of the most interesting developments in psychiatric medicine in decades.

Diagnosis

The Diagnostic and Statistical Manual of Mental Disorders V (DSM-5) released by the American Psychiatric association is referred to many in the mental health industry as their Bible, the go to guide for defining a mental illness and the book that sets the bar for a diagnosis of a particular illness. The guide is occasionally revised to update it with the latest scientific findings in the field and since the last revision of DSM-4 appeared 13 years ago in 2000, an update was due. These revisions are often contentious, but few people could have foreseen just how controversial this update would prove to be.

Changing the definitions of a disease is controversial because a disease is often a part of a person’s perceived identity and changing the name or even removing that definition altogether can be an enormous shock to a person’s sense of who they are. It is also complicated by the slightly less abstract concept of money; if the measures of what counts as a disease is moved, then a patient could find themselves deprived of drugs and treatment as their insurance may no longer cover it. Even though both of these played a part in the DSM-5 controversy, neither was the main bone of contention.

Medicalization

The main objection to the DSM-5 is the lowering of the bar in certain diseases so that, some claim, ordinary behaviours now could be classified as mental illnesses. In the DSM-4, an alteration in mental state in response to bereavement was one of the “homeostatic reactions to major life events” that should not be regarded as a mental illness. The DSM-5 has removed the provision for bereavement, a move that some mental health professionals are equating with medicalizing grief. Another lightening rod has been Disruptive Mood Disregulation Disorder (DMDD), the diagnosis for which is 3 tantrums per week for a year. Some have argued that ‘DMDD’ is normal behavior in children and that stigmatizing these children with a mental illness diagnosis is unhelpful and unnecessarily treating them with drugs may expose them to side effects.

Revolution

One of the most interesting responses to the DSM-5 is not reactionary, but potentially revolutionary. In the past few decades there has been an enormous amount of work done in the fields of neuroscience, genetics and molecular biology etc. in comparing the normal physical states of the brain to those of people diagnosed with specific illnesses to discover the molecular basis of mental illness. New criteria that have been development for the last 3 years by the National Institute of Mental Health (NIMH) threaten to turn this system on its head. The NIMH Research Domain Criteria (RdoC) asserts that in the past genes and pathways seem to have been only moderately associated with certain categories of mental illness and so a more logical course of action may be to focus on the underlying mechanisms and create the disease classifications based on these. The NIMH compares current psychiatric diagnosis to a doctor trying to diagnose a feverish patient by asking them about the character of their fever. Pointing out the ridiculousness of this situation, the RdoC gives an outline of how mental illnesses can be classified by their underlying mechanisms instead. This gives psychiatry a firmer foothold in empirical evidence and may eventually result in more definitive diagnoses based on scientifically validated markers, rather than subjective experiences.

This is a paradigm shift, a total re-envisioning of how mental diseases are classified. There will certainly be resistance to RdoC as it is far more challenging than any DSM revision. It will undoubtedly lead to new perspectives on research in neurology and promises to be a brand new angle of attack on diseases of mental illness. The NIMH is adamant that these criteria are not aiming to replace the DSM, but rather to complement it in what it aims to do; give patients, doctors and researchers the information they need on mental illnesses. Although the ability to fully understand pathways in the brain is a distant prospect, with the USA and the EU having invested $1billion and €1billion respectively in mapping the brain, the NIMH have chosen a prime moment to announce these criteria in order to frame future neurological work.

Regulation

The FDA uses the DSM as a guide to licensing drugs for mental illness. In keeping with the division in the DSM of disorders into behavioural and cognitive, the FDA separated its Division of Neuropharmacological Drug Products into the Division of Neurological Products (DNP) and the Department of Psychiatry Products (DPP). Since some cognitive and behavioural disorders often share some neurological features, a diagnostic system based on these features and not symptoms may provide some problems in deciding which department’s purview a disorder will fall under. In a 2011 article in the Journal of Neuropsychiatry & Clinical Neuroscience, then FDA official Dr Thomas Laughren lamented that this parting of behavioural from cognitive meant that behavioural problems in cognitive illnesses (such as in Alzheimer’s Disease) and cognitive problems in behavioural diseases (such as in schizophrenia) were left untreated and unresearched as they were considered secondary. Since these ‘orphan symptoms’ of disease have a neurological basis, ideally a neurological-based classification system would lead to a holistic approach to treatment where they are not ignored. It remains to be seen how or if the FDA and other regulatory bodies will change their requirements in drug licensing in response to a more biomarker-based approach.

This version of the DSM at the very least has helped to draw attention to the progress that has been made in bioscience and neurological research in recent years. With the RDoC gaining attention, the identification of neurological targets for pharmacological intervention will be a number one priority and may help attract more public funding into neuropharma R&D.

The issues surrounding this are likely to be the primary focus of the psychiatric and neuropharma industries over the next years and it will be interesting to see how the DSM will respond to the controversy and whether they will move to align themselves more closely with RDoC.

[image from wikimedia]

What do you think about the DSM-5? How might researchers work more closely with the pharma industry? Can RDoC revitalise neuropharma R&D? Let us know in the comments below