Diagnosis and Classification of Schizophrenia

Question 1

Diagnosis of SZ

Answer 1

Diagnosis of schizophrenia is based on classification systems such as the DSM-5 (used mainly in the US) and the ICD-11 (used internationally, including the UK). These systems differ in criteria.

For instance, DSM-5 requires at least one positive symptom (e.g., hallucinations, delusions) to be present for diagnosis, while ICD-11 may allow diagnosis on the basis of negative symptoms like avolition or speech poverty. Such differences contribute to inconsistency in diagnosis.

Question 2

Major issues with SZ classification

Answer 2

A central issue in diagnosis is reliability, particularly inter-rater reliability — the degree to which different researchers reach the same diagnosis for a given individual. Another major issue is validity, which refers to whether schizophrenia is a real, distinct disorder that we are accurately identifying.

Validity is challenged by symptom overlap with other disorders like bipolar disorder, and by comorbidity, where schizophrenia frequently co-occurs with other conditions such as depression or substance use disorders. Additionally, cultural and gender bias may affect who gets diagnosed and how.

Question 3

AO3

Answer 3

A major issue is the low inter-rater reliability of schizophrenia diagnoses. In a study, two psychiatrists independently assessed 100 patients. Using the DSM, one diagnosed 26 and the other 13 with schizophrenia; with the ICD, the figures were 44 and 24. Such disparity highlights inconsistency across both systems and clinicians, reducing confidence in the diagnostic process.

Another significant concern is symptom overlap. For instance, delusions and avolition are also present in bipolar disorder and depression. This makes it difficult to distinguish schizophrenia from other mental illnesses, reducing diagnostic validity. This can lead to wrongly attributing behaviours to the disorder, leading to incorrect treatment.

Another issue is comorbidity. Buckley et al. (2009) found that 50% of schizophrenics also suffered from depression, and 47% also had substance abuse issues. This raises the question: are we diagnosing a distinct condition, or labelling a collection of symptoms that actually stem from multiple interacting disorders?

Cultural and gender biases further undermine validity. For example, research shows that people of Afro-Caribbean descent are up to nine times more likely to be diagnosed with schizophrenia in the UK than white British individuals. This cannot be explained biologically and is likely due to cultural misinterpretation or unconscious bias. Gender bias is also evident: men may be over diagnosed because they tend to display more negative symptoms, which may be mistakenly see as SZ symptoms