IB Validity and diagnosis

What does the term validity mean to you? When considering the validity of a diagnosis, we have to ask does the person REALLY have the condition they have been diagnosed with? May be they do not need a diagnosis at all? May be they have been diagnosed with a condition when in fact they don’t have that condition, in fact maybe they don’t have any psychiatric condition at all (Type 1 error) or maybe they have been deemed to have no condition at all, when in fact they perhaps do have a certain condition, (Type 2 error).

Can you think of any reason why it might be hard to make a VALID diagnosis? Think about how psychiatrists collect information about service users in order to make their decisions, think about cognitive psychology, how do people process information (SELECT, ORGANISE and INFER), what ideas do you about why a psychiatrist may find it hard to make a valid diagnosis.

Is psychiatric diagnosis an objective process? Think about how we might diagnose a broken leg or cancer? How does this differ to making a psychiatric diagnosis?

So, what does VALIDITY mean in this context?

In the context of diagnosis, validity refers to how accuracy, meaningfulness and usefulness of a diagnosis (Willerton et al 2013). An unreliable diagnosis, will not be a valid one, yet a reliable diagnosis does not mean the diagnosis is necessarily valid. We are going to learn about a few specific types of validity to help us discuss this topic in more detail. You should be able to use at least 3 of the following types of validity in your oral and written work.

  • descriptive validity
  • aetiological validity
  • concurrent validity
  • predictive validity

Types of validity: types-of-validity-improved

On the revision area for this topic there is a nice long essay, which combines all the different things that you need to know about regarding validity and reliability of diagnosis. Read the essay in order to find out about factors which can affect the validity of diagnosis. You will find out about:

  • Reification
  • Top down processing
  • Reading-in Syndrome
  • Cognitive biases/Reconstructive Memory
  • Selective Remembering
  • The Primacy Effect
  • Rapport
  • Barriers to Communication

Make notes from the essay and once you feel more confident with the terms, use the sheet here to match the term to its definition, use colour coding  to match them up:



In order to test your knowledge of the different areas that you have looked at so far, try the following exercise, you need to say whether the scenarios relate to:

  • good or bad reliability: test-rest or inter-rater reliability
  • good or bad validity; concurrent, predictive, descriptive or aetiological


r-and-v-mix-and-match-2 (answer sheet)

Using research evidence to evaluate validity of diagnosis

In the  A Level textbook you can read about a study by Brown (2014) which is about the validity of the diagnosis of Anorexia using the DSM5; read the study and make a brain map to record the details; decide on some headings to structure your brainmap; what is the nature of each piece of information that you are being given, e.g. the first heading might be: problems with DSM5 for diagnosing Anorexia.

Think:  What type of errors (type 1 and 2) might be creeping into diagnosis of anorexia due to change in DSM 5? Explain your choices.

Now, you need to look back at the studies that you sorted into reliability and validity. You should have had the following three studies in the validity pile:

  • Kim Cohen
  • Hoffman
  • Lee

Read each study carefully and work out which types of validity are being demonstrated in the study. You could sue the studies to help explain the concepts if you need to. You could also use the studies as part of your evaluation of the validity of the DSM.

Finally do a little more reading from your textbook to answer the following question: How has section 3 (particularly) of the DSM 5 helped to improve the validity of diagnosis?

The following articles will be helpful to enrich your answers: