Schizophrenia - AO1 and AO3

Diagnosis and classification:

AO1:

• ICD-10 requires two or more negative symptoms.
• DSM-5 requires negative and positive symptoms.
• Both have dropped the diagnosis of subtypes due to inconsistency of diagnosis.
• Positive symptoms (additional behaviours or experiences):
  • Hallucinations.
  • Delusions.
• Negative symptoms (absence of usual behaviours or experiences):
  • Speech poverty.
  • Avolition.

AO3:

• Jakobsen et al (2005) found high external reliability between ICD and DSM diagnoses.
• Osorio et al (2019) found high inter-rater reliability in diagnoses made using the DSM.
• Cheniaux et al (2009) found low criterion validity, as in the same sample of 100 patients, psychologists diagnosed 68 of them with schizophrenia when using the ICD, but only 39 using the DSM.
• Buckley et al (2009) found high levels of co-morbidity with schizophrenia and other conditions like depression and substance abuse. This could suggest that maybe schizophrenia doesn't actually exist as an individual condition.
• Gender bias. Far more men are diagnosed with schizophrenia. This may be due to genetic reasons, or maybe women get more support from friends and family for it.
• Culture bias. Schizophrenia is not viewed as negative in some cultures, so the stigma that comes with it in Western cultures is harmful. Additionally, there is an overinterpretation of symptoms in black British people (Escobar 2012).
• Symptom overlap. Schizophrenia has overlapping symtpoms with many other mental disorders, so some patients may be diagnosed incorrectly, or schizophrenia might not even be a separate disorder.

Biological explanations:

AO1:

• Risk of schizophrenia increases in line with genetic similarity to a relative with the disorder.
  • Gottesman (1991) found a concordance rate of 48% in MZ twins, compared to 17% in DZ twins.
• There may be candidate genes which code for schizophrenia.
  • Evidence suggests that schizophrenia is polygenic and aetiologically heterogenous.
  • The most likely genes are those which code for neurotransmitters, such as dopamine.
  • Ripke et al (2014) conducted a meta-analysis on genome-wide studies of schizophrenia and found 108 separate genetic variations which code increase risk for schizophrenia.
• Mutation in parental DNA may also cause schizophrenia.
• This mutation may come from things like radiation, poison or viral infection.
  • Brown et al (2002) found a positive correlation between paternal age and risk of schizophrenia.
• Neural correlates like dopamine may cause schizophrenia.
• Hyperdopaminergia is an abnormally high level of dopamine in the subcortex.
  • Seeman (1987) found that DA reducing antipsychotics caused Parkinsons-like symptoms.
• Hypodopaminergia is an abnormally low level of dopamine in the cortex - Davis et al (1991).
  • Low levels of DA in the prefrontal cortex may cause negative symptoms.
  • Cortical hypodopaminergia may cause subcortical hyperdopaminergia.
• Genetic variations and stressful early experiences may make someone more vulnerable to hypodopaminergia and hyperdopaminergia - Howes et al (2017).

AO3:

• Gottesman is supporting evidence as the study shows that risk increases with genetic similarity to a schizophrenic family member.
• Tienari et al (2004) found that biological children of schizophrenics are more likely to develop schizophrenia, even if they are adopted by a family of non-schizophrenics.
• Curran et al (2004) found that amphetamines increase dopamine and also worsen schizophrenics symptoms.
• Reductionist…