There are two classification systems which you need to know for the exam: the DSM and the ICD. Classification systems aim at categorising diseases and identifying the symptoms of them. This helps us diagnose disease, and are a great step forward from the four D’s, which we mentioned in the previous post.

Diagnostic and Statistical Manual of Mental Disorders (DSM)

The DSM is one of these classification systems, developed in the US in 1952. Although the specification states that you need to know the DSM-IVR or the DSM5, I’ll write about both here because it’s useful for the issue and debate of ‘how psychological understanding has developed over time’. 


The DSM IVR is a revised version of the DSM IV, released in 2000. The revolutionary aspect of this manual was the introduction of 5 “axes” on which a patient was measured. These included personality problemsgeneral medical conditionsenvironmental stress and global functioning. The psychologist would take all of these into account when diagnosing the patient.


The DSM-IVR attempted to tackle mental health diagnosis in a more holistic way by considering everything from general medical conditions, to environmental stress. This could be seen as a positive because it’s taking into account more of the contributing factors.

However, the axes made the manual much more difficult to use and less friendly to those who did use it. This explains why it lost popularity in comparison with the DSM-III and why they removed the axes in the DSM5.


The DSM5 removed the 5 axes and created a categorical system – similar to the previous DSM-III and the ICD. It’s also preparing to be revised much more frequently to ensure it stays up-to-date. It also removed unnecessary diagnoses and grouped together similar ones (Such as grouping autism into a spectrum). Additionally, it attempted to keep up with social advances, such as reflecting cultural differences (For example, in some cultures a panic attack is charactarised by difficulty breathing but in others it consists of uncontrollable crying).


Firstly, it can be commended for becoming more accessible and user-friendly by removing the confusing axes. This improves the usefulness of the classification system because if it’s easier to use, it’s more likely to be used correctly and lead to accurate diagnoses.

Additionally, the DSM5 was developed with the intention of standardising with the ICD – making them both easier to use together. This could be seen as an improvement of the reliability of the manual.

However, it’s been argued that the DSM5 was developed with the influence of large pharmaceutical corporations. This could have encouraged them to define more behaviours as abnormal to allow more drugs to be developed.


International Classification of Disease (ICD10)


The ICD is a manual which covers all disease, not just mental illnesses. All of the mental illness come under the ‘F’ section. It then further categorises the illnesses into groups. For example: F32.0.00 is mild depression without somatic (physical) symptoms.


It could be said that the ICD10 is reliable due to its standardisation and clear definitions of diseases. It’s easy to use the manual to narrow down the symptoms to a specific diagnosis.

It’s also advantageous because it is continuously updated to reflect new updates in medicine. It has already been revised 10 times, and will continue to be revised in the future.

Validity and Reliability of Mental Illness Diagnosis


An advantage is that the DSM-IV in particular has become very holistic, ensuring that the psycholigist looks beyond whether the patient merely has the symptoms, but they also take into account their situation and background.

Additionally, both of the classification systems respond to the latest advances in research to provide accurate diagnoses in response to new research. For example, in both the ICD and DSM, homosexuality used to be listed as a mental illness.

The British Psychological Society (BPS) criticise the DSM because they feel it was designed to make patients fit the diagnosis, not to make the diagnoses fit the patient. They feel that the system should be built from the bottom up, starting with experiences, problems and symptoms.

Some people believe that the DSM has a tendancy to diagnose mental illnesses too easily. For example, Binge Eating Disorder will lead to people being diagnosed who are just greedy. This is expensive and can also harm the patient if the incorrect drugs are administered.


An advantage of the ICD and DSM is that they clearly define what it means to have each mental illness and what defines each one. This can be useful in finding the correct treatment for each patient and is also useful in research to agree on what counts as anorexia beforehand, for example.

Brown et al (2001) tested the reliability of the DSM-IV and found that there was a high level of agreement between two psychologists in two seperate interviews.

Andrews et al (1999) found a 68% agreement between the DSM and ICD, which is relatively low. However it’s important to point out that this was in 1999, the latest revisions had not been released of either of them.