Issues in the diagnosis & classification of schizophrenia

• For a diagnosis of schizophrenia to be reliable it must show consistency and agreement across diagnosing clinicians i.e. the same set of symptoms must be given the same diagnosis regardless of who is doing the diagnosing 
• Inter-rater reliability refers to the above point: if more than one clinician is diagnosing the same patient then they should both/all agree as to the diagnosis 
• Issues with reliability occur when (as does happen) clinicians disagree as to the diagnosis
• Unreliable diagnosis may happen if clinicians do not use the same diagnostic tools e.g. one clinician uses the DSM and other uses the ICD, regardless of year of publication of both of these manuals
• Validity of diagnosis refers to the ‘realness’ of what is being measured i.e. is the classification system being used to diagnose the patient actually set up to diagnose schizophrenia or does it fall short of this criterion? 
• An invalid diagnosis may occur if a clinician, having reviewed the patient’s symptoms, gives a diagnosis of an illness that does not actually fit those symptoms e.g. Sybil believes that she has multiple personalities and her doctor diagnoses schizophrenia (the correct diagnosis should be dissociative identity disorder)

Research which investigates reliability & validity in diagnosis

• Santelmann et al. (2016) conducted a meta-analysis of 25 studies with a total sample of 7912 patients diagnosed by different raters and found that reliability of schizophrenia diagnosis had consistently lower inter-rater reliability than the diagnosis of major depressive disorder and bi-polar disorder
• Rosenhan (1973) tested the validity of schizophrenia diagnosis in a field experiment in which he and eight confederates reported false symptoms and were all (but one) admitted to mental hospitals with a diagnosis of schizophrenia 

Do all patients receive a diagnosis that is both reliable and valid?

• Co-morbidity is when one patient may present symptoms (and/or be suffering from) more than one mental illness
• Patients with schizophrenia are at an increased risk for the development of depression as the two illnesses may share a common aetiology and/or genetic basis (Samson & Wong, 2015) 
• One of the difficulties in diagnosing a co-morbid patient is trying to ascertain the extent of one illness over another particularly when there is symptom overlap (e.g. Is this depression or is it part of patient X’s schizophrenia?)
• Symptom overlap is exactly what it sounds like: when two or more illnesses present with some of the same symptoms e.g. avolition (a negative symptom of schizophrenia) overlaps with symptoms of depression - lethargy, lack of motivation, neglecting  personal hygiene etc.
• One of the major stumbling blocks for clinicians when faced with symptom overlap is that the DSM and the ICD use different criteria to classify the same symptoms e.g. the DSM might produce a diagnosis of schizophrenia whereas the ICD diagnosis might be bi-polar disorder for the same set of symptoms

Research which investigates co-morbidity & symptom overlap

• Newson et al. (2021) - a meta-analysis of 107,349 that DSM-5 diagnostic criteria do not sufficiently distinguish between schizophrenic symptoms and those of co-morbid/overlapping disorders such as depression
• Buckley et al. (2009) found that schizophrenia has the following co-morbidities: 50% for depression; 47% for substance abuse disorder; 29% for PTSD; 23% for OCD; 15% for panic disorder

• Gender bias in diagnosis refers to any instances of a person being diagnosed according to their gender as opposed to the set of symptoms they present with 
• An example to illustrate the above bullet point might be that a woman is not diagnosed with schizophrenia even when she presents with symptoms as the clinician may view her as a ‘hysterical female’ rather than taking her symptoms seriously (an example of alpha bias)
• Gender bias may also occur when a clinician does not take a patient’s gender into account when making a diagnosis e.g. male models of health are used to diagnose a woman
• Clinicians may also not pay enough attention to the fact that the risk factors for developing schizophrenia are different for male and females so there should be no ‘one size fits all’ approach (an example of beta bias)
• Culture bias in diagnosis refers to any instances of a person being diagnosed according to their culture as opposed to the set of symptoms they present with 
• An example to illustrate the above bullet point might be that an African patient is not diagnosed with schizophrenia by a British clinician, as the clinician may misunderstand or disregard their culture-specific symptoms e.g. ukuthwasa which has some symptom overlap with schizophrenia i.e. the clinician does not know what to diagnose and so may end up ignoring all of the patient’s symptoms
• Culture bias may also occur when a clinician does not take a patient’s culture into account when making a diagnosis e.g.if the Western biomedical model is used to diagnose people from non-Western cultures it may (and does) result in African patients being over-diagnosed with schizophrenia due to a lack of understanding of culture-bound syndromes e.g. belief in witchcraft

Research which investigates gender & culture bias in diagnosis

• Hambrecht et al. (1993) - found that males and females are equally at risk of developing schizophrenia but schizophrenia is underdiagnosed in women 
• Schwartz et al. (2019) found evidence that African Americans are 2.4 times more likely to be diagnosed with schizophrenia compared with White individuals which points to culture bias in the diagnostic process and cultural insensitivity on the part of White clinicians

Link to Issues & Debates:

Mental illness is a socially sensitive topic so researchers must be particularly mindful of how their research will be interpreted and commented on once it is published. Gender and culture are ‘hot topics’ in the media generally so the ways in which research is conducted and presented must not be seen to perpetuate stereotypes or to encourage prejudice and discrimination of people based on their gender, sexuality, culture or ethnicity.