Schizophrenia

Two diagnostic materials used for schizophrenia

DSM

ICD-10

Positive symptoms of schizophrenia

Excess of normal functions → pathological excess or distortion = add to person’s personality

• Delusions

• Hallucinations

Positive symptoms of schizophrenia: delusions

Irrational false beliefs

Remain unchanged even when individual is presented with conflicting evidence

Completely disconnected from reality → often appears bizarre to others

Positive symptoms of schizophrenia: hallucinations

Sensory perceptions → occur in absence of external stimulus

Vivid + involuntary + perceived as being located in external space (rather than in individual’s imagination)

Can happen in any of the senses = any modality

Negative symptoms of schizophrenia

Loss of normal functions → often persist more + more resistant to traditional antipsychotic treatments

• Avolition

• Speech poverty

Negative symptoms of schizophrenia: avolition

Total lack of motivation to initiate + persist in self-directed + purposeful activities = apathy

Signs of avolition = Andreasen identified clear indicators ~ failure to maintain personal hygiene, lack of persistence in work or school

Negative symptoms of schizophrenia: speech poverty

Alogia

Significant reduction in amount or fluency of speech

Reflects disruption in thought process rather than physical inability to speak

Comorbidity

Occurrence of two or more distinct clinical conditions in single patient

Schizophrenia rarely exists in isolation = complicates “descriptive validity” of disorder

Schizophrenia comorbidity: Buckley et al

A → quantify prevalence of comorbid psychiatric conditions in schizophrenic patients

P → review clinical data from patients diagnosed with schizophrenia

F → 50% = comorbid depression, 47% = substance abuse, 29% = PTSD, 23% = OCD

C → high comorbidity = suggests scz may not be distinct category → may lead to inconsistent diagnosis + inefficient treatment

Schizophrenia comorbidity: AO3

Reduces validity in diagnosing + treating schizophrenia → due to overlapping symptoms

Bias in scz diagnosis: gender bias

Men : women scz diagnosis = 4:1

Diagnostic criteria = applied inconsistently between men vs women → often leads to under-diagnosis in females

Suggests validity of diagnosis of scz = poor

Gender bias in diagnosis: Loring and Powell

A → test if patient’s gender influences psychiatrist’s diagnosis

P → 290 psychiatrists evaluated identical case studies → only gender was changed

F → patient labelled male = 56% diagnosed scz vs patient labelled female = 20% diagnosed scz

C → women = under-diagnosed → often maintain higher interpersonal functioning = masks severity of symptoms to clinicians

Bias in scz diagnosis: culture bias

Misinterpretation of cultural norms as scz symptoms

Assuming British cultural standards are ‘correct’

• Afro-Caribbean descent = 7 times more likely to be diagnosed vs white citizens ~ Cochrane (in Britain)

• Western clinicians → label “hearing voices” = hallucination

  • Spiritual norm in some African cultures

• Leads to unfair institutionalisation of minority groups

Symptom overlap

Different disorders share identical clinical features.

Patients could be diagnosed with multiple conditions simultaneously → depends on which symptoms clinician prioritises

Ambiguity = results in misdiagnosis + delays in appropriate pharmacological intervention

Symptom overlap: Cheniaux et al

A → investigate reliability + validity of scz diagnosis

P → two psychiatrists independently assessed 100 patients → using DSM + ICD-10

F → diagnosed 26 with scz using DSM + 44 using ICD vs diagnosed 13 with DSM + 24 with ICD

C → lower inter-rater reliability is low

Biological approach to schizophrenia

Asserts scz = physical illness

Focuses on:

• Genes

• Dopamine

• Brain structure

Biological approach to schizophrenia: genetic correlates

Polygenic = many genes contribute → no single gene responsible

• Large number of genes = ones that affect dopamine neurotransmitter production

Aetiologically heterogeneous = different genetic combinations can produce same symptoms

Ripke → found 108 separate genetic variations associated with scz

Biological approach to schizophrenia: genetic explanations → twin studies

Gottesman → mz twins = 48% concordance rate vs dz twins = 17% concordance rate

• Indicates genetic factor involved → not purely biological

• MZ twins = 100% same genetic data + similar environment

• DZ twins = ~50% same genetic data + similar environment

• Difference between concordance rate should be entirely due to genetic factors → not demonstrated in this study

Biological approach to schizophrenia: genetic explanations → adoption study

Tienari → Finnish adoption study = longitudinal study with 19000 ppts

• Children of scz mothers vs matched sample of children with non-scz mothers

• Results = 7% children of scz mothers developed scz vs 1.5% of controls

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Biological approach to schizophrenia: dopamine hypothesis

Imbalance of neurotransmitter of dopamine → drives symptoms of scz

Hyperdopaminergia (excess)

Hypodopaminergia (deficit)