Diagnosis and classification of schizophrenia

• Schizophrenia

  Serious complex mental disorder
• Schizophrenia is experienced by 1% of the world's population
• Schizophrenia is more commonly diagnosed in men than women
• Schizophrenia is more commonly diagnosed in cities compared to countryside
• Schizophrenia is more commonly diagnosed in working-class than middle-class people
• Schizophrenia is more commonly diagnosed between ages 18-35
• Symptoms of schizophrenia can interfere with everyday tasks so many who are diagnosed may be homeless or hospitalised
• Classification of schizophrenia

  Does not have a single defining characteristic, made up of a cluster of symptoms which may appear unrelated
• Types of schizophrenia symptoms

  • Negative symptoms
  • Positive symptoms
• World Health Organisation's International Classification of Diseases edition 10 (ICD-10) requires 2 or more negative symptoms to be present for a diagnosis
• American Psychiatric Association Diagnostic and Statistical Manual edition 5 (DSM-5) requires 1 positive symptom to be present for diagnosis
• Subtypes of schizophrenia (recognised by ICD-10)


  • Paranoid schizophrenia
  • Hebephrenic schizophrenia
  • Catatonic schizophrenia
• Positive symptoms

  Describes something extra/an addition
• Hallucinations

  Sensory stimuli that have either no basis in reality or are distorted perceptions of things that are there
• Hallucinations can be related to any senses, e.g. may see distorted facial expressions to people and animals that are not there
• Delusions

  Also known as paranoia, delusions are irrational beliefs
• Common delusions involve being Jesus, political or religious figures, or being persecuted by governments or aliens
• Negative symptoms

  Reduction or loss of normal function
• Avolition

  A difficulty to keep up with or begin goal oriented tasks, reduction in interests due to a lack of motivation/energy
• Signs of avolition (Andreasen 1982 et al.)


  • Poor hygiene and grooming
  • Lack of persistence in school or work
  • Lack of energy
• Speech poverty


  Reduced frequency and quality of speech
• ICD-10 recognises speech poverty as a negative symptom, while DSM-5 focuses more on speech disorganisation where speech becomes incoherent
• Reliability of schizophrenia diagnosis is poor, with inconsistency between diagnoses using DSM vs ICD criteria
• Validity of schizophrenia diagnosis is poor, with over-diagnosis in ICD or under-diagnosis in DSM
• Schizophrenia is commonly diagnosed with co-morbid conditions like depression, substance abuse, PTSD, and OCD, which challenges the classification and diagnosis process
• There is considerable overlap between the symptoms of schizophrenia and other conditions like bipolar disorder, calling into question the validity of the classification and diagnosis
• Men have been more likely to be diagnosed with schizophrenia than women since the 1980s, potentially due to gender bias in diagnosis
• African Americans and English individuals from Afro-Caribbean descent have a significantly higher chance of being diagnosed with schizophrenia, potentially due to cultural bias in diagnosis
• Peter Buckley (2009)

  •  Concluded that around half the people with a schizophrenia diagnosis also have diagnosed depression (50%) and substance abuse (47%)  
  • PTSD also occurs in 29% of cases and OCD in 23%  
• Peter Buckley (2009) - conclusions

  • This challenged both the classification and diagnosis process of schizophrenia 
  • In terms of diagnosis - because there such a high correlation between depression and schizophrenia diagnosis are psychiatrists just bad at telling the two conditions apart  
  • In terms of classifications – is may be that sever schizophrenia looks like depression and vice versa - this may be that it's better to see them as just one condition 
  • This paints a confusing picture and is a large weakness of diagnosis and classification of schizophrenia 
• Longenecker et al (2010) - gender bias in diagnosis

  • Reviewed studies for the prevalence of schizophrenia. Found that men since the 1980s were more likely to be diagnosed with schizophrenia than women.  
  • Prior to 1980s there had been no difference in the frequence of diagnosis between the genders   
  • Could be because men are more genetically vulnerable to the development of the condition of because of gender bias  
• Cotton et al (2009) - gender bias in diagnosis

  • Found that women compared to men function better.  
  • It’s this high functioing which may explain why women are underdiagnosed when men with similar symptoms are diagnosed  
  • Their better overall function may lead to buas within the psychological practioner and cause them to underdiagnose patients
• Cultural bias in diagnosis

  Potential bias that can occur when diagnosing mental health conditions across different cultures
• Some of the positive symptoms of schizophrenia like hearing people talk is more normalised and common in certain cultures
• In their unique culture those voices are seen as their ancestors and communication with them is heavily encouraged
• When experiences are recoded to a psychiatrist from a different culture

  They may be seen as bizarre and irrational, leading to a diagnosis of schizophrenia
• Escobar (2012): 'Overwhelmingly white psychiatrists tend to over interpret their symptoms and distrust the honesty of Afro-Caribbeans during their diagnosis'
• Reliability - 🙁  

  • Thinking about consistency between diagnosis  
  • Inter-rater reliability – Extent to which two or more mental health professionals arrive at the same    
  • Elie Cheniaux et al. (2008) - had two psychiatrics independently diagnose 100 people using DSM and 1CD criteria  
  • Inter-rater reliability was poor  
  • One psychiatrist diagnosing 26 with schizophrenia according to DSM and 44 according to ICD  
  • The other diagnosing 13 using DSM and 24 according to ICD  
• Validity - 🙁 

  • Describes the extent to which we are measuring what we are intending to measure  
  • One standard way of assessing validity of a schizophrenia diagnosis is criterion validity  
  • Which looks at how different Sysmon's arrive at the same diagnosis for the same person  
  • Considering Cheniaux et al. (2008) results above we can see that schizophrenia is more likely to be diagnosed using ICD compared to DSM  
  • Thu suggests that schizophrenia is either over-diagnosed in ICD or under-diagnosed in DSM  
  • Poor validity and a weakness of diagnosis for schizophrenia