Classification & Diagnosis (AQA A-Level Psychology): Revision Notes
Classification & Diagnosis
Understanding schizophrenia
Schizophrenia is a severe mental disorder where contact with reality and insight are impaired. It represents an example of psychosis and affects approximately 1% of the world population. The condition is more commonly diagnosed in men than women, more frequently in urban areas than rural settings, and more often in working-class rather than middle-class populations.
The symptoms can severely interfere with daily functioning, leading many individuals to experience homelessness or hospitalisation. This makes schizophrenia not just a personal health issue but also a significant social and economic concern.
Classification of mental disorder refers to the process of organising symptoms into categories based on which symptoms cluster together in people with mental disorders. This systematic approach helps clinicians identify and diagnose conditions more effectively.
Classification systems
Two major systems exist for classifying schizophrenia: the World Health Organisation's International Classification of Disease edition 10 (ICD-10) and the American Psychiatric Association's Diagnostic and Statistical Manual edition 5 (DSM-5). These systems differ slightly in their classification criteria.
Under DSM-5 guidelines, one of the so-called positive symptoms (delusions, hallucinations, or speech disorganisation) must be present for diagnosis, whereas two or more negative symptoms are sufficient under ICD-10 criteria. This difference can lead to significant variations in diagnosis rates between systems.
ICD-10 recognises several subtypes of schizophrenia. Paranoid schizophrenia is characterised by powerful delusions and hallucinations but relatively few other symptoms. Hebephrenic schizophrenia involves primarily negative symptoms, whilst catatonic schizophrenia is distinguished by disturbance in movement, leaving the person immobile or alternatively overactive. Previous DSM editions also recognised these subtypes, but this classification has been dropped in DSM-5.
Positive symptoms
Positive symptoms are atypical symptoms experienced in addition to normal experiences. They represent extra experiences beyond what most people would consider typical.
Hallucinations
Hallucinations are unusual sensory experiences that either have no basis in reality or are distorted perceptions of actual stimuli. These experiences are not related to events in the environment but rather to what the senses are detecting internally. For example, individuals may hear voices that are either talking to them or commenting on their behaviour, often critically. Hallucinations can affect any sense, including seeing distorted facial expressions or occasionally perceiving people or animals that are not present.
Delusions
Delusions, also known as paranoia, involve irrational beliefs that have no foundation in reality. Common forms include delusions of grandeur involving important historical, political or religious figures such as Jesus or Napoleon. Delusions also commonly involve feelings of persecution, perhaps by government agencies or aliens, or beliefs about having special powers. Another category concerns bodily delusions, where people believe that parts of their body are under external control.
Delusions can influence behaviour in ways that make sense to the individual but appear bizarre to others. Although most people with schizophrenia are not aggressive and are more likely to be victims than perpetrators of violence, some delusions can occasionally lead to aggression.
Negative symptoms
Negative symptoms involve the loss of usual abilities and experiences. These represent a reduction or absence of normal functioning.
Avolition
Avolition, sometimes called 'apathy', describes difficulty in beginning or maintaining goal-directed activity. People with schizophrenia often show sharply reduced motivation to carry out everyday activities. Andreason (1982) identified three key signs: poor hygiene and grooming, lack of persistence in work or education, and lack of energy.
Speech poverty
Speech poverty involves changes in speech patterns, with ICD-10 recognising it as a negative symptom due to its emphasis on reduction in the amount and quality of speech in schizophrenia. This is sometimes accompanied by delays in the person's verbal responses during conversation.
However, DSM-5 places greater emphasis on speech disorganisation, where speech becomes incoherent or the speaker changes topic mid-sentence. This is classified in DSM-5 as a positive symptom, whilst speech poverty remains categorised as negative.
Evaluation of classification and diagnosis
Reliability
Reliability means consistency, with inter-rater reliability being particularly important in diagnosis. This measures the extent to which different mental health professionals arrive at the same diagnosis for identical individuals.
Research Example: Cheniaux et al. (2009) Reliability Study
Two psychiatrists independently diagnosed 100 people using both DSM and ICD criteria:
- Psychiatrist 1: 26 diagnoses (DSM), 44 diagnoses (ICD)
- Psychiatrist 2: 13 diagnoses (DSM), 24 diagnoses (ICD)
This demonstrates poor inter-rater reliability and significant inconsistency between diagnostic systems.
Validity
Validity concerns whether we are measuring what we intend to measure. Criterion validity examines whether different assessment systems arrive at the same diagnosis for the same person. Looking at the Cheniaux et al. study figures shows that schizophrenia is much more likely to be diagnosed using ICD than DSM criteria. This suggests either over-diagnosis in ICD or under-diagnosis in DSM, both indicating poor validity.
Co-morbidity
Co-morbidity describes the phenomenon where two or more conditions occur together. If conditions frequently co-occur, this questions the validity of their separate diagnosis and classification, as they might actually represent a single condition.
Schizophrenia commonly appears alongside other conditions. Research by Buckley et al. (2009) found that around half of people diagnosed with schizophrenia also have depression (50%) or substance abuse (47%). Post-traumatic stress disorder occurred in 29% of cases and OCD in 23%.
This presents challenges for both classification and diagnosis - if half those diagnosed with schizophrenia also have depression, perhaps clinicians struggle to distinguish between the conditions, or if severe depression resembles schizophrenia and vice versa, they might be better understood as a single condition.
Symptom overlap
Considerable overlap exists between schizophrenia symptoms and other conditions. Both schizophrenia and bipolar disorder involve positive symptoms like delusions and negative symptoms like avolition. This again questions the validity of both classification and diagnosis.
Under ICD criteria, a person might receive a schizophrenia diagnosis, whilst many of the same individuals would be diagnosed with bipolar disorder according to DSM criteria. This overlap even suggests that schizophrenia and bipolar disorder may not represent two different conditions but one.
Gender bias in diagnosis
Research by Longenecker et al. (2010) reviewing prevalence studies concluded that since the 1980s, men have been diagnosed with schizophrenia more frequently than women (prior to this period, no difference appeared to exist).
This pattern might simply reflect men being more genetically vulnerable to developing schizophrenia. However, another explanation involves gender bias in diagnosis. Women typically function better than men, being more likely to work and maintain good family relationships (Cotton et al., 2009).
This higher functioning may explain why some women have not received schizophrenia diagnoses where men with similar symptoms might have been diagnosed. Better interpersonal functioning may bias practitioners to under-diagnose schizophrenia, either because symptoms are masked by good interpersonal functioning, or because the quality of interpersonal functioning makes cases seem too mild to warrant diagnosis.
This potential under-diagnosis of women suggests poor validity in the diagnostic process, as procedures may work effectively for only one gender.
Cultural bias in diagnosis
African Americans and English people of Afro-Caribbean origin are diagnosed with schizophrenia several times more frequently than white people. Given that rates in Africa and the West Indies are not particularly high, this pattern is almost certainly not due to genetic vulnerability. Instead, diagnosis appears affected by cultural bias.
Several factors may contribute to this disparity. Positive symptoms such as hearing voices may be more acceptable in African cultures due to cultural beliefs about communication with ancestors, making people more willing to acknowledge such experiences. When reported to psychiatrists from different cultural backgrounds, these experiences are likely interpreted as bizarre and irrational.
Additionally, research by Escobar (2012) suggests that predominantly white psychiatrists may tend to over-interpret symptoms and distrust the honesty of Afro-Caribbean patients during diagnosis.
This over-diagnosis of schizophrenia in certain ethnic groups suggests poor validity, as the diagnosis may be confounded by cultural beliefs and behaviours in patients, or by prejudicial attitudes among mental health practitioners.
Remember!
Key Points to Remember:
- Classification systems like ICD-10 and DSM-5 have different criteria for diagnosing schizophrenia, with ICD-10 requiring fewer positive symptoms than DSM-5
- Positive symptoms (hallucinations and delusions) are experiences beyond normal functioning, whilst negative symptoms (avolition and speech poverty) represent losses of normal abilities
- Reliability issues exist as different clinicians often disagree on diagnoses, whilst validity problems arise from inconsistent diagnoses between classification systems
- Co-morbidity and symptom overlap with conditions like depression and bipolar disorder question whether these represent truly separate conditions
- Gender and cultural bias in diagnosis suggest that classification systems may work better for some groups than others, undermining their overall validity