The DSM, the ICD and the CCMD are classification systems that psychiatrists use to diagnose clients.  Classification systems provide checklists of affective, behavioural, cognitive and somatic symptoms which guide the diagnostic process.  But determining which symptoms is not enough to make a diagnosis. Both the intensity and the duration of the symptoms are important.  Although there are clear strengths to using such a system, there are also disadvantages.

Classification systems provide checklists of symptoms as well as recommendations for treatment to guide a psychiatrist in the diagnosis of a client.  The DSM is an American system produced by the APA and the ICD is a more international classification system, sponsored by the WHO and put together by psychiatrists from around the globe. The CCMD is the Chinese diagnostic manual which, like the DSM, may be considered ethnocentric.

Knowledge and understanding shown of the different classification systems and some reference to their differences.

One supposed strength of using a classification system is that it provides a standardized process of diagnosis that should lead to reliable results.  That is, two psychiatrists using the same guide should be able to diagnose the same client with the same disorder. Although this is logical, it is not necessarily the case.  In a study by Di Nardo et al (1993) two clinicians each diagnosed the same 267 people seeking treatment for anxiety disorders. They found high reliability for obsessive-compulsive disorder (.80) but very low reliability for assessing generalized anxiety disorder (.57).  This is because although “excessive worry” is considered a symptom of the disorder, it difficult to objectively measure.  The study challenges the argument that classification systems increase reliability, but it also used the DSM III.  The new DSM 5 may prove to be more reliable, but at this point, this still needs to be tested.

Another strength of using a classification system is that it provides a standardized, operationalized definition on which research can be based.  When carrying out research on Major Depressive Disorder, for example, if we know that the diagnosis of depression was based on the DSM IV, we know how that disorder was defined and we can assume that all participants in the study met certain criteria.  Without such definitions, it would be impossible to carry out valid or reliable research in abnormal psychology.

A clear argument about the advantage of using a classification system to do research.

Although the classification systems should create a standardized process for all patients, there are other factors that may influence diagnosis, regardless of the use of such a system. The use of the diagnostic checklist is based on a combination of observed or self-reported symptoms.  One problem, for example, is that just the process of diagnosis may make a client uncomfortable.  This may lead to a behaviour called “reactivity” in which the client displays distress or other “abnormal behaviours,” which the psychiatrist may then link to a disorder. Self-reported data is also subject to distortion – with clients often showing optimism bias (e.g. saying that they drink less alcohol than they do) or the peak-end rule, reporting the most recent behaviour rather than “average rates of behaviour.” This may misrepresent their actual behaviour or distress.

A final disadvantage of using a classification system is that it could be considered culturally biased.  The DSM is an American diagnostic tool that, although used outside of the United States, was developed by American psychiatrists. An example of how this may influence diagnosis was seen in Bolton’s study of the prevalence of depression among the Rwandan population after the genocide.  Using the DSM IV, Bolton’s team found very high rates of depression among the Rwandans.  But this makes sense.  The criteria for depression in the DSM is based on social norms in the United States, not a country that has just survived genocide. Using an emic approach, Bolton worked with local community leaders to learn how they knew which people were coping well with the tragedy, and who should be diagnosed as having depression.  When the symptoms identified by the local healers were used to adapt the checklists for the local community, the prevalence of depression was in line with global standards.

Classification systems have the noble goal of providing the same level of diagnosis and treatment to everyone, regardless of where they live or their social class.  They also establish definitions that help facilitate research.  However, in spite of their goal of high standardization, the reliability of diagnosis remains difficult to achieve.  In spite of the use of such systems, objective data remains difficult to collect and there may be too many variables that need to be taken into account to allow for consistently valid diagnosis.

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