In order to be valid, the diagnoses must identify a distinct condition that has different symptoms from other conditions and that is likely to progress in a certain way and respond to one treatment over another. A valid diagnosis for a mental disorder is more difficult than for a physical disorder because of a lack of objective physical signs. To be valid, the DSM also has to be reliable.
This refers to whether or not a classified disorder is actually a good indicator of what you’re really trying to measure, for example, in operationalising a disorder such as depression by drawing a list of symptoms and features, you begin to lose some understanding of the real nature of the disorder so the DSM becomes invalid.
DSM lacks this
This is when the results of a study matches the result of another study done at the same time, so this would mean that if a diagnosis made using the DSM arrives at the same mental disorder that another diagnosis has, it is likely to have concurrent validity.
Diagnosis is valid if it predicts the course of the illness accurately e.g. if diagnosed as schizophrenic periods of mania should not occur. Also: The treatment/therapy put in place after diagnosis should be effective if the diagnosis is valid e.g. antipsychotics should reduce the symptoms of schizophrenia.
I.e. The clinician's role in interpreting the DSM.
Assuming cultural norms
Relies on patient honesty
To be reliable as a diagnostic classification system, there would have to be consistency with the DSM. This means that the DSM is reliable if the clinicians using it consistently arrive at the same diagnoses as each other. The term inter-rater reliability is used to describe the extent to which different clinicians agree on the same diagnosis for the same patient.
Traditionally, reliability is calculated mathematically, often using a measure known as positive predictive value (PPV). The PPV of a disorder shows the reliability, taking the example of depression, of the DSM with that disorder; so if depression had a PPV value of 80, this means that 80% of diagnosed depression patients will have the same subsequent diagnosis when re-assessed.
Affected by culture
Brown et al., Some boundary issues
Kirk & Kutchins
Can the DSM can be used as a valid tool outside the USA? Systems such as DSM tend to be culturally biased as they do not take into account different values in different countries, so people outside western cultures may be misdiagnosed.
Cultural differences with US
Omits some culture-bound syndromes
Clinicians may be unwilling to give culturally sensitive diagnoses e.g. schizophrenia in Japan (Sato 2006)
The current version of DSM is still unsatisfactory in terms of cross cultural applicability according to Escobar & Vega (2006) because of its strong western bias.
Ignores religious factors
Risk of mis-diagnosis