The World Health Organization's International Standard Classification of Diseases, Injuries and Causes of Death - ICD-10

One of the first actions of the World Health Organization, immediately after its formation in 1948, was to publish a comprehensive list of the world's diseases and illnesses. The International Standard Classification of Diseases, Injuries and Causes of Death (or 'ICD'), predictably included psychological and psychiatric 'conditions'. This effectively ensured that these kinds of problems were seen as the responsibility of medicine and ensured that diagnosis, classification and categorisation was the method of choice. This diagnostic manual has been extensively revised over the years, and we are now using ICD-10, the tenth and most recent revision.4 ICD-10 is, technically at least, the international standard classification system, recommended for administrative and epidemiological purposes and forms the basis of statistical procedures in the UK National Health Service.

American Psychiatric Association's Diagnostic and Statistical Manual - DSM-5

The immediate post-war period also saw the publication of the American Psychiatric Association's Diagnostic and Statistical Manual - DSM.5 This was based on the administrative scheme used by the US Army in World War II. As with ICD, the DSM system has been revised and re-edited over time, meaning that the current edition is the fifth - DSM-5. The DSM franchise is, of course, very widely used in the USA. Because DSM is used for research classification as well as epidemiological and statistical purposes, and because most researchers want to publish their results in US-based, English language publications, it has become standard practice for researchers, even in Europe, to use DSM criteria. The two systems, ICD and DSM, have run in parallel ever since and there is considerable overlap, and increasing convergence, between the two systems.

The fact that there are two separate classification systems is somewhat embarrassing for the diagnostic model. It is embarrassing because if there is an objective illness of 'depression' (or 'schizophrenia' or 'attention deficit hyperactivity disorder' or whatever) it would seem odd if social factors such as whether we follow an American or European tradition were to determine its existence. Scientists and clinicians recognise this, and one of the principal reasons for the latest revision of DSM (from DSM-IV to become DSM-5) was to permit easier 'read-across' between the two systems. There are even mechanisms for translating DSM codes into ICD codes. However, the two codes are not identical. A good illustration of this is in the diagnostic criteria for depression - which is, of course, very common indeed. The DSM-5 diagnostic guidelines are more complex, more detailed and more prescriptive than the ICD-10 criteria. It is possible for a person to meet the ICD-10 criteria for a diagnosis of depression, but fail to meet the DSM-5 criteria. For example, if you have been experiencing low mood, a loss of interest and enjoyment and reduced energy for the past three weeks, you would meet the ICD-10 criteria for a diagnosis of 'depressive episode'. But unless you are also experiencing weight loss or sleep disturbance, feel agitated, worthless or guilty, are unable to concentrate or having thoughts of suicide, you would not qualify for the equivalent DSM-5 diagnosis of 'major depressive episode'. That might be rare (many people who meet the ICD-10 criteria will, in fact, meet the DSM-5 criteria), but illustrates some of the confusion.

There have been many specific changes as DSM-IV has been revised to become DSM-5. One controversial change6 was the decision to drop a specific exclusion criterion. The fourth edition suggested that people should not be diagnosed with 'major depression' if they had been recently bereaved. In technical language, it was not appropriate to record a diagnosis of 'major depressive episode' if (in technical language) ' ... the symptoms are not better accounted for by Bereavement ... '. We all feel low when a loved one has died and so, the logic went, we don't need to label people in that situation as 'ill'. But this requirement was dropped in DSM-5. That means it now is possible to receive a diagnosis of 'major depressive episode' if you experience low mood following the death of a loved one. Many people worldwide were concerned by this development and the idea that someone grieving for a loved one could be diagnosed with a 'mental illness'. I agree. But here are - within, strictly within, the logic of psychiatric diagnosis - reasons for this odd decision. First, the ICD-10 doesn't have an exclusion for bereavement, so it could be argued that this brings the two manuals closer together. And, technically - and this will be a surprise to some people - diagnostic manuals are not concerned with the causes of or reasons for a person's problems. If a person is experiencing low mood, they are experiencing low mood. The fact that a loved one has died is a very good reason for such low mood, but it doesn't mean the low mood isn't there.

In my opinion, then, the problem is not really whether bereavement is, or is not, included as an exclusion criterion for a diagnosis of 'major depressive episode'. My concern is a larger one. I simply don't think we should be asking these kinds of questions in the first place.

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