Over the years, Vincent van Gogh’s mental illness has been classified in 30 different ways by over 150 different physicians, not just those who originally treated him. It is becoming clear that, in the classification of madness, this is far from an isolated example. Amongst the ranks of both psychiatrists and clinical psychologists are those who argue for a radical rethink.
Richard P. Bentall, a clinical psychologist and Professor of Experimental Clinical Psychology at the University of Manchester, recently published ‘Madness Explained‘, an attempt to wrestle descriptions of madness away from rigid categorisation as well as provide an alternative. In this, the first of a series of posts, I will discuss Bentall’s criticisms of the major categories of mental illness.
The Categorisation of Madness
Traditional psychiatric practice has placed madness in a number of different categories. Two well-known examples of these categories are bipolar disorder – what used to be called manic depression – and schizophrenia. These categories, along with a host of others, are used by many mental health professionals as both a shorthand description of mental illness, and a guide to treatment.
Reliability and Validity
There are two simple criteria used by scientists to measure, amongst other things, whether a system of diagnosis is useful: these are its reliability and its validity. Reliability refers to whether different doctors give the same diagnosis to the same person with the same symptoms. The validity of a diagnosis is a measure of whether it describes what it is supposed to describe. In other words, if you were a doctor and I told you someone you are about to meet is schizophrenic, then, broadly, you would not be surprised by the symptoms they exhibited.
Bentall argues psychiatric diagnoses are neither particularly reliable, nor particularly valid. Here is why.
Reliability studies of different classification systems are many and varied. One typical study is that carried out by, amongst others, Robert Spitzer, a strong proponent of the DSM classification system. This study found only modest agreement between specially trained psychiatrists of the same patients – and these results were obtained under ideal conditions, probably not representative of the average busy clinician.
To pick any single study as representative of the whole is not very scientific. Bentall, however, who has evaluated many of them, argues that, in general, the research has been less than convincing. Many studies even fail to reach the minimum statistical criteria for reliability.
While there are 201 different diagnoses in the DSM-IV, arguably the most established distinction in psychiatric classification systems is between schizophrenia and bipolar disorder. To question this distinction is not merely to attack a straw man – the difference is fundamental. Nevertheless the research has seriously questioned whether there is a clear dividing line between the two diagnoses.
Kendell & Gourlay (1970) examined the symptoms of nearly 300 patients with diagnoses of either schizophrenia or manic depression – now referred to as bipolar disorder. If the prevailing system of classification is correct then we should see two distinct groups of symptoms. What the study actually found was a continuum of symptoms, with most patients falling in the middle. They had some symptoms typical of schizophrenia and some typical of manic depression. Subsequent research has provided similar evidence of the poor validity of current systems of classification.
Why, then, is it important that classification systems are valid and reliable? What are the alternatives? Can madness be cured? All questions for future posts…
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Further related discussion on MindHacks.