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- identifying and classifying abnormal behaviour
- done based on a set of symptoms, the patient's self-reports, observations, and other factors


types of diagnostic manuals

- DSM (Diagnostic and Statistical Manual of Mental Disorders)

- ICD (International Classification of† Diseases)



Diagnostic and Statistical Manual of Mental Disorders
- published by the American Psychiatric Association
- attempts to describe disorders in clear terms so that two clinicians referring to the system would probably agree with the diagnosis it suggests
- categorizes and lists the symptoms required for a diagnosis to be given, but does not identify causes
- encourages a multiaxial approach: a diagnosing clinician should consider not only the symptoms but also physiological conditions and/or social issues
- diagnosis with DSM encourages and takes advantage of modern breakthroughs

e.g. Alzheimer’s disease and attention-deficit-hyperactivity disorder (ADHD) can now be diagnosed with brain-imaging tech



International Classification of† Diseases
- published by WHO (World Health Organization)
- more commonly used internationally than DSM
- WHO intended for it to be used to standardize recordings of cause of death
- ICD covers a wide range of diseases and conditions for the sake of classification rather than diagnosis, and so covers causes of conditions as well as symptoms
- one chapter categorizes mental disorders appears very similar to DSM because the authoring teams consult with each other


ethical considerations when using diagnostic systems

- unreliable
- incorrect approach: medical approach should not be used for psychological problems
- incorrect usage: in the Soviet Union, the diagnosis of schizophrenia was given more liberally than in USA at the time, leading to the incarceration and treatment of individuals who might have been better understood under a more specific diagnostic system
- lack of cultural considerations: ethnic minorities and women may not be treated equally with others in terms of the chances of receiving a correct diagnosis, level of understanding offered by practitioners, and treatment offered


define validity in the context of a diagnosis

- the correctness of a diagnosis – does a person really have the disorder?
- a valid diagnostic system should allow doctors to identify the difference between someone who has a particular disorder and someone who does not

studies: Rosenhan et al. (1973)


validity issues

- R.D. Laing: diagnostic process uses inappropriate approach (shouldn't be medical approach)
- Thomas Szasz: medical approach fosters a misconception of the nature of a psychological disorder
- Peters et al. (1999): DSM and ICD don't always agree in terms of symptoms required for a diagnosis

Study: Rosenhan et al (1973)


validity issues: Laing on the medical approach

R. D. Laing:
- diagnosis uses a medical model, but psychiatric diagnosis is more of a social fact than a medical one
- psychiatrists cannot diagnose based on biological facts, as there are no reliable biological tests to diagnose most psychological disorders, only guidance about categorizing behaviour, thoughts and emotions


validity issues: Szasz on the medical approach

Thomas Szasz:
- wrong to use a mental illness metaphor to describe
behaviour that does not conform to expectations
- while there are some biological correlates of behaviour, it is reductionist to assume that mental conditions (e.g. depression, schizophrenia) are biological diseases
- biological causes have not yet been established for most psychological disorders
- can you "catch" depression in the same way that you catch the common cold?
- important to remember that terms like ‘depression’ and ‘schizophrenia’ are simply labels given to a set
of behaviours, emotions, or thoughts
- while some believe that an underlying condition called depression causes severe unhappiness, depression IS the unhappiness (along with other symptoms), rather than the cause of it


Rosenhan et al. (1973) - overview

- Rosenhan and 11 other colleagues and friends (no diagnosed disorders) went to psychiatric hospitals and reported that they had been hearing voices
- apart from questions relating to these experiences, they answered all questions honestly
- most of them were admitted to the hospital and were given a diagnosis of schizophrenia
- upon being admitted, all pseudopatients ceased complaining of any symptoms
- their normality was never detected by the nursing staff
- when taking notes about what happened in the hospital, hospital staff recorded that this patient’s writing was excessive and abnormal
- when they walked the corridors because they were bored they were accused of obsessive pacing
- when they were released, they were labelled with "schizophrenia in remission"


Rosenhan et al. (1973) - follow-up

- staff at another hospital claimed they wouldn't have been fooled by Rosenhan’s pseudopatients
- they were invited to estimate how many times Rosenhan attempted to trick them in this way during a 3-month period
- confidently, at least one staff member estimated that 41 out of the 193 people who were admitted during the test
period were pseudopatients
- Rosenhan had sent none: all were genuine patients


Rosenhan et al. (1973) - conclusion

- validity is difficult to achieve
- yet, achieving a valid diagnosis is ethically necessary


Rosenhan et al. (1973) - in defense of the diagnostic process...

first study
- ethical responsibility: hospitals have an ethical responsibility to investigate odd behaviour, and even if the hospital staff thought they were faking, they still had to investigate in order to protect the community and protect the people from themselves
- even if the doctors did not believe hearing voices was genuine, walking into a hospital and lying about hearing voices is still abnormal behaviour

second study:
- many real dysfunctional patients fake their symptoms
e.g. a non-depressed person who fakes being depressed can be considered to be dysfunctional


Rosenhan et al. (1973) - evaluation

- highly influential study: prompted investigation into the reliability and validity of diagnosis and its consequences

- ethical issues of original: deception of hospital staff, but was necessary to expose the flaws of the diagnostic process to benefit future patients
- ethical issues of follow-up: the patients that the staff believed to be imposters may not have received treatment they needed


validity issues: agreement between different systems

- criterion-related validity: all systems should agree with each other in terms of measures of the phenomenon in question
i.e. poor validity occurs when a person can be diagnosed with one system but not with another system by the same practitioner or group of practitioners

Peters et al. (1999):
- found only moderate agreement between DSM and ICD
- DSM is more careful about diagnoses; it requires the presence of distress or impairment to functioning in the person being diagnosed


define reliability in the context of a diagnosis

- how stable the diagnosis is – do different doctors agree about the diagnosis? does the diagnosis stay the same over time?

study: Nicholls et al. (2000)


reliability tests

- inter-rater reliability: ask > 1 practitioner to make a diagnosis with the the same diagnostic system; if they make the same decision, the system is reliable
- test–retest reliability: ask 1 practitioner to diagnose a patient during different times (e.g. on two different days).


Nicholls et al. (2000)

- asked 2 practitioners to use inter-rater reliability with DSM, ICD, and GOS (Great Ormond hospital's system)
- diagnosed 81 children who complained of eating problems
- reliability was measured based on rates of diagnoses agreements between the 2 practitioners
- result: GOS > DSM > ICD
- technical problem with DSM: less than half of the children diagnosed using DSM could be diagnosed with
a classified eating disorder
- GOS was most reliable probably because it was specifically developed with children in mind

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