Diagnosis and classification

• Schizophrenia= a severe mental disorder where contact with reality and insight are impaired
• Positive symptoms = additional experiences beyond those of ordinary experiences. They include hallucinations and delusions.
• Hallucinations = unusual sensory experiences. Some hallucinations are related to events in the environment whereas others bear no relationship to what the senses are picking up from the environment. Hallucinations can be experienced in relation to any sense (e.g. seeing distorted facial expressions or hearing voices).
• Delusions = irrational beliefs, also known as paranoia- these can take a range of forms. Common delusions involve being an important historical, political or religious figure. Delusions also commonly involve being persecuted, perhaps by government or aliens. Another class of delusions concerns the body. A person may believe they are under external control. Delusions can make a person behave in ways that make sense to them but are bizarre to others.
• Negative symptoms = involve the loss of usual abilities and experiences. They include speech poverty and avolition.
• Speech poverty = reduction in the amount or quality of speech- sometimes accompanied by a delay in a person's verbal responses during conversation. Nowadays, however, more emphasis is placed on speech disorganisation in which speech becomes incoherent or the speaker changes topic mid-sentence.
• Speech disorganisation is classified as a positive symptom in DSM-5 whilst speech poverty remains a negative symptom.
• Avolition (or apathy) = finding it difficult to begin or keep up with goal-directed activity (actions performed in order to achieve a result). People with schizophrenia often have sharply reduced motivation to carry out a range of activities. Nancy Andreasen identified three signs of avolition: poor hygiene and grooming, lack of persistence in work or education and lack of energy.
• The two major systems for the classification of mental disorder are the World Health Organisation's International Classification of Disease and the American Psychiatric Association's Diagnostic and Statistical Manual edition 5 (DSM-5). These differ slightly in their classification of schizophrenia. For example, in the DSM-5 system one of the positive symptoms must be present for diagnosis whereas two or more negative symptoms are sufficient under ICD.
• Both DSM-5 and ICD-10 have dropped subtypes because they tended to be inconsistent (e.g. someone with a diagnosis of paranoid schizophrenia would not necessarily show the same symptoms a few years later.)
• A strength of the diagnosis of schizophrenia is its reliability. A psychiatric diagnosis is said to be reliable when different diagnosing clinicians reach the same diagnosis for the same individual (inter-rater reliability) and when the same clinician reaches the same diagnosis for the same individual on two occasions (test-retest reliability). Prior to DSM-5, reliability for schizophrenia diagnosis was low but it has now improved. This means we can be sure that the diagnosis of schizophrenia is consistently applied.
• A limitation of the diagnosis of schizophrenia is its validity. Validity concerns whether we assess what we are trying to assess. One way to assess validity of a psychiatric diagnosis is criterion validity. Cheniaux et al. had two psychiatrists independently assess the same 100 clients using ICD-10 and DSM-IV criteria and found that 68 were diagnosed with schizophrenia under the ICD system and 39 under DSM. This suggests that schizophrenia is either over- or under diagnosed according to the diagnostic system. Either way this suggests that criterion validity is low.
• Validity:

  Osório reported excellent reliability for diagnosis of schizophrenia in 180 individuals using the DSM-5. Pairs of interviewers achieved inter-rater reliability of +97 and test-retest reliability of +92.
• However, in the Osório et al. study reported above there was excellence agreement between clinicians when they used two measures to diagnose schizophrenia both derived from the DSM system. This means that the criterion validity for diagnosing schizophrenia is actually good provided it takes place within a single diagnostic system.
• Another limitation of schizophrenia diagnosis is its co-morbidity with other conditions. If conditions occur together a lot of the time then this calls into question the validity of their diagnosis and classification because they might actually be a single condition. Schizophrenia is commonly diagnosed with other conditions. Buckley et al. found that about half of those diagnosed as schizophrenic also had a diagnosis of depression or substance abuse. This means schizophrenia may not exist as a distinct condition.
• A further limitation of schizophrenia is the existence of gender bias. Since the 1980s men have been diagnosed with schizophrenia more commonly than women. A possible explanation for this is that women are less vulnerable than men, perhaps because of genetic factors. However it seems more likely that women are underdiagnosed because they have closer relationships and hence get support. This leads to women with schizophrenia often functioning better than men. This under diagnosis is a gender bias and means women may not be receiving treatments and services that might benefit them.
• Another limitation is culture bias. Some symptoms of schizophrenia, particularly hearing voices, have different meanings in different cultures. British people of African-Caribbean origin are up to nine times as likely to receive a diagnosis as white British people although people living in African-Caribbean countries are not, ruling out a genetic vulnerability. The most likely explanation is culture bias in diagnosis by psychiatrists from a different cultural background. This means British African-Caribbean people may be discriminated against by a culturally-biased diagnostic system.
• A final limitation is symptom overlap with other conditions. There is considerable overlap between the symptoms of schizophrenia and the symptoms of other conditions. For example, schizophrenia and bipolar disorder both involve positive symptoms (delusions) and negative symptoms (avolition). In terms of classification this suggests that schizophrenia and bipolar disorder may not be two different conditions but variations of a single condition. In terms of diagnosis it means that schizophrenia is hard to distinguish from bipolar disorder. So both its classification and diagnosis are flawed.
• What is a final limitation mentioned in the study material?

  Symptom overlap with other conditions
• What is the relationship between schizophrenia and other conditions?

  There is considerable symptom overlap
• How do schizophrenia and bipolar disorder symptoms compare?

  Both involve positive and negative symptoms
• What positive symptom is shared by schizophrenia and bipolar disorder?

  Delusions
• What negative symptom is shared by schizophrenia and bipolar disorder?

  Avolition
• What does the symptom overlap suggest about schizophrenia and bipolar disorder?

  They may be variations of a single condition
• What challenge does symptom overlap create for diagnosis?

  It makes schizophrenia hard to distinguish from bipolar disorder
• What does the overlap in symptoms indicate about the classification of schizophrenia and bipolar disorder?

  Both classification and diagnosis are flawed
• What is a strength of the diagnosis of schizophrenia?

  Its reliability
• What does it mean for a psychiatric diagnosis to be reliable?

  Different clinicians reach the same diagnosis
• What is test-retest reliability?

  The same clinician diagnoses the same individual twice
• How was the reliability of schizophrenia diagnosis prior to DSM-5?

  It was low
• How has the reliability of schizophrenia diagnosis changed with DSM-5?

  It has improved
• What does improved reliability in schizophrenia diagnosis imply?

  Diagnosis is consistently applied