Clinical Psychology: Classification Systems - DSM
The diagnostic and statistical manual of mental disorders (DSM) was first published in 1952 and was based on a classification system that helped identify disorders experienced by World War 2 soldiers. The DSM has since then been revised to include over 300 mental and behaviour disorders arranged into 22 categories.
The DSM-5 was published in 2013 and is divided into three sections:
Section 1 – Explains how to use the system.
Section 2 – Section 2 outlines the disorders based on our current understanding of the underlying causes and similarities between the symptoms. There is also a dimensional assessment added – which allows for an independent measure of the symptoms.
Section 3- This section focuses on the introduction and suggestion of new disorders, which may require further investigation. The impact of culture is also discussed in this section in order to ensure that the clinician knowns how to approach each patient.
How do you Make a Diagnosis?
In order to make a diagnosis using the DSM-5 majority of data will be gathered via unstructured clinical interviews. Clinicians may also use structured interviews such as the Beck Depression Inventory. Clinicians start by ruling out disorders which do not fit the individuals symptoms, this should leave behind a set number of disorders and clinicians can chose the one which best fits the individual. Usually, diagnosis can take a few hours however they could take as long as weeks and even months in more severe cases.
How is Reliability Measured?
The reliability of the DSM is measured using Cohens Kappa (introduced by Spitzer). Cohens Kappa measures how many people received the same diagnosis when assessed and re-assessed. This can be done at a later time known as test-retest reliability or it can be done by another clinician known as inter-rater reliability.
How is Validity Measured?
Validity refers to how true a piece of data is? There are four main types of validity:
Descriptive Validity – If two people that have been diagnosed with the same disorder, experience similar symptoms then this is descriptive validity.
Aetiological Validity – When individuals diagnosed share similar casual factors, we can say they have aetiological validity.
Concurrent Validity – If a clinician uses multiple techniques to diagnose a patient's disorder and they both come to the same diagnosis then it has concurrent validity.
Predictive Validity – If we can predict correctly what happens after someone has been diagnosed, we can say it has predictive validity.
Reliability of the DSM
Field trials using the DSM-5 have demonstrated high level of inter-rater reliability between clinicians when diagnosing a variety of disorders. Regier et al. (2013) found that three disorders (including PTSD) had kappa values of 0.60 to 0.70 which is very good. Whilst seven more disorders including schizophrenia have had kappa values of 0.40 to 0.59 which is rated as overall good. However, what is significant about these values is that there has been significant changes to the criteria need to diagnose disorders such as PTSD (which has seen major revisions in the symptoms needed to be diagnosed) and it shows that clinicians have adapted well!
A weakness on the other hand is that standards have been falling over the last 35 years. Cooper (2014) found how the DSM-5 task force classified levels as low as 0.2-0.4 as ‘acceptable’. (Major Depressive Disorder (MDD) was found to be one of the most unreliable disorder with a kappa value of 0.28 (Regier 2013)).
Validity of the DSM
Kim-Cohen et al. (2005) found concurrent validity of Conduct Disorder (CD) by conducting interviews on mothers and their children, having teachers complete questionnaires, and observing the children’s antisocial behaviour. Aetiological validity was also shown with common factors identified such as: male, low income, and parental psychological disorders. Predictive validity was also shown with 5-year-old CD kids being more prone to displaying behavioural and educational difficulties at 7.
A weakness of the DSM is that psychologists feel like the DSM still lacks validity. They argue that the DSM does not actually explain what causes the symptoms and diagnoses, hence it gives us a label but no reason as to what created it.
References/ Further Reading:
Psychopathology– Wikipedia - https://en.wikipedia.org/wiki/Psychopathology#The_four_Ds